00-01-course-guide.md

<!---
Current Directory : /in28Minutes/git/java-a-course-for-beginners
-->

# Course Guide

## 01-IntroductionToJavaProgrammingWithJShell

## Steps
- Step 00 - Getting Started with Programming
- Step 01 - Introduction to Multiplication Table challenge
- Step 02 - Launch JShell
- Step 03 - Break Down Multiplication Table Challenge
- Step 04 - Java Expression - An Introduction
- Step 05 - Java Expression - Exercises
- Step 06 - Java Expression - Puzzles
- Step 07 - Printing output to console with Java 
- Step 08 - Printing output to console with Java - Exercise Statements
- Step 09 - Printing output to console with Java - Exercise Solutions
- Step 10 - Printing output to console with Java - Puzzles
- Step 11 - Advanced Printing output to console with Java 
- Step 12 - Advanced Printing output to console with Java - Exercises and Puzzles
- Step 13 - Introduction to Variables in Java
- Step 14 - Introduction to Variables in Java - Exercises and Puzzles
- Step 15 - 4 Important Things to Know about Variables in Java
- Step 16 - How are variables stored in memory?
- Step 17 - How to name a variable?
- Step 18 - Understanding Primitive Variable Types in Java
- Step 19 - Understanding Primitive Variable Types in Java - Choosing a Type
- Step 20 - Java Assignment Operator
- Step 21 - Java Assignment Operator - Puzzles on Increment, Decrement and Compound Assignment
- Step 23 - Java Conditionals and If Statement - Introduction
- Step 24 - Java Conditionals and If Statement - Exercise Statements
- Step 25 - Java Conditionals and If Statement - Exercise Solutions
- Step 26 - Java Conditionals and If Statement - Puzzles
- Step 27 - Java For Loop to Print Multiplication Table - Introduction
- Step 28 - Java For Loop to Print Multiplication Table - Exercise Statements
- Step 29 - Java For Loop to Print Multiplication Table - Exercise Solutions
- Step 30 - Java For Loop to Print Multiplication Table - Puzzles
- Step 31 - Programming Tips : JShell - Shortcuts, Multiple Lines and Variables TODO Move up
- Step 32 - Getting Started with Programming - Revise all Terminology

## Exercises

#### Expressions
- Write a Java expression to calculate the number of minutes in a day.
- Write a Java expression to calculate the number of seconds in a day.

#### Printing Output to Console
- Print ```Hello World``` onto the console.
- Print ```5 * 3```, as is.
- Print the calculated value of ```5 * 3```.
- How do we now approach the Multiplication Table print problem, for the number ```5```?
- Print the number of seconds in a day, using the ```System.out.println``` method.
- Do a syntax revision for the code that you write for each of the above exercises. In your code, identify the following elements:
   * Numeric and string literals
   * Expressions
   * Operators
   * Operands
   * Method calls

#### Advanced Printing Output to Console
- Print the following output by passing 4 values 5, ,6, 7 and sum of  the numbers: ```5 + 6 + 7 = 18``` 

#### Variables
- Create three integer variables ```a```, ```b``` and ```c```. 
   * Write a statement to print the sum of these three variables.
   * Change the value of ```a```, and then print this sum.
   * Then again, change the value of ```b``` and print this sum.

#### If Statement
- Create four integer variables ```a```, ```b```, ```c``` and ```d```. - Write an ```if``` statement to print if the sum of ```a``` and ```b``` is greater than the sum of ```c``` and ```d```.
- Store three numerical values as proposed angles of a triangle in integer variables ```angle1```, ```angle2``` and ```angle3```. Create an ```if``` statement to state whether these three angles together can form a triangle. _Hint: A triangle is a closed geometric figure with three angles, whose sum must  exactly equal ```180 degrees```._
- Have a variable store an integer. Create an ```if``` statement to find out if it's an even number._Hint: Use operator ```%```._

#### For Loop
- Repeat the entire process at arriving at the Multiplication Table Print problem, now for the number ```7```. Start with fresh JShell session, if you're still using an existing one for quite some time (Rinse, and repeat!).
- Use the final solution to print Multiplication Tables for ```6``` and ```10```.
- Print the integers from ```1``` to ```10```.
- Print the integers from ```10``` to ```1```.
- Print the squares of the integers from ```1``` to ```10```.
- Print the squares of the first ```10``` even integers.
- Print the squares of the first ```10``` odd integers.

## Code Snippets

```java
3*4
System.out.println(3*4)
System.out.println("5 * 2 = 10")
3.0/2
System.out.println("5 * 2")
System.out.println(5 * 2)
System.out.println("Hello World")
System.out.println(5*3)
System.out.println("5 * 3")
System.out.println(5*3)
System.out.println("5 * 1 = 5")
System.out.println("5 * 2 = 5")
System.out.println("5 * 3 = 5")
System.out.println("24 * 60 * 60")
System.out.println(24 * 60 * 60)
System.out.println("Hello World")
System.out.println("Hello     World")
System.out.println(24   *    60    *    60)
System.out.println("Hello World")
System.out.println("HelloWorld")
System.out.println("hello world")
System.out.println("hello \"world")
System.out.println("hello \"world")
System.out.println("hello n world")
System.out.println("hello \n world")
System.out.println("hello \nworld")
System.out.println("hello\nworld")
System.out.println("hello\tworld")
System.out.println("hello \\ world")
System.out.println("hello \\\\ world")
Math.random()
System.out.println("hello \n world")
Math.min(23,45)
Math.min(23,4)
Math.max(23,4)
System.out.println("5 * 2 = 5")
System.out.println("5 * 2 = 10")
5*2
System.out.printf("5 * 2 = 10")
System.out.printf("5 * 2 = 10").println()
System.out.printf("5 * 2 = 10 %d", 5*2).println()
System.out.printf("5 * 2 = %d", 5*2).println()
System.out.printf("%d %d %d", 5, 7, 5 * 7).println()
System.out.printf("%d * %d = %d", 5, 7, 5 * 7).println()
System.out.printf("%d + %d + %d = %d", 5, 6, 7, 5 + 6 + 7).println()
System.out.printf("%d + %d + %d = %d", 5, 6, 7).println()
System.out.printf("%d + %d + %d", 5, 6, 7).println()
System.out.printf("%d + %d + %d", 5, 6).println()
System.out.printf("%d + %d + %d", 5, 6, 7, 8).println()
System.out.printf("Print %s", "Testing").println()
System.out.printf("%d + %d + %d", 5.5, 6.5, 7.5).println()
System.out.printf("%f + %f + %f", 5.5, 6.5, 7.5).println()
System.out.printf("5 * 2 = 10")
System.out.printf("%d * %d = %d", 5, 2, 5 * 2).println()
System.out.println("5 * 2 = 10")
System.out.printf("%d * %d = %d", 5, 2, 5 * 2).println()
System.out.printf("%d * %d = %d", 5, 1, 5 * 1).println()
System.out.printf("%d * %d = %d", 5, 2, 5 * 2).println()
System.out.printf("%d * %d = %d", 5, 3, 5 * 3).println()
System.out.printf("%d * %d = %d", 5, 4, 5 * 4).println()
number = 11
number
number = 12
number
number2 = 100
System.out.printf("%d * %d = %d", 5, 4, 5 * 4).println()
System.out.printf("%d * %d = %d", 5, i, 5 * i).println()
i
5 * i
i = 2
System.out.printf("%d * %d = %d", 5, i, 5 * i).println()
i = 3
System.out.printf("%d * %d = %d", 5, i, 5 * i).println()
i = 10
System.out.printf("%d * %d = %d", 5, i, 5 * i).println()
System.out.printf("a + b + c = a+b+c").println()
System.out.printf("%d + %d + %d = %d", a, b, c ,a+b+c).println()
a = 50
System.out.printf("%d + %d + %d = %d", a, b, c ,a+b+c).println()
b = 60
System.out.printf("%d + %d + %d = %d", a, b, c ,a+b+c).println()
int newVariable;
newVariable
int undeclaredVariable;
undeclaredVariable
5 * undeclaredVariable
a = 100
a = c
int noOfGoals;
int NoOfGoals;
int score;
short s;
float f = 4.0f;
float f2 = 4.5f;
double dbl = 4.5;
i = j
i
j
i = j
i = j * 2
i = i * 2
i = i + i
i = i - i
i = i - 1
i++
i
i++
i
i--
number = number + 1
number++
number--
++number
--number
number--
number
i = i + 2
i += 2
i -= 1
i *= 5
i
i /= 4
i %= 2
;
long l = 6_000_000_000l;
short numberOfGoals;
numberOfGoals++
numberOfGoals
numberOfGoals++
numberOfGoals
long populationOfTheWorld;
double average;
char ch = 'A';
ch = 'B'
char grade = 'C';
grade = 'A'
grade
boolean isEven;
isEven = true
boolean isPrime;
boolean isItRainingToday;
boolean areYouEnjoyingTheCourse;
areYouEnjoyingTheCourse = true
System.out.printf("%d * %d = %d", 5, i, 5*i);
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
i = 7
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
i = 10
i < 5
i > 5
i <= 5
i <= 10
i >= 10
System.out.println("i is less than 5");
i
if (i<5)
   System.out.println("i is less than 5");
i
i = 4
if (i<5)
   System.out.println("i is less than 5");
int number1 = 5;
int number2 = 7;
if (number2>number1)
System.out.println("number2 is greater than number1");
number2 = 3
if (number2>number1)
System.out.println("number2 is greater than number1");
int a = 1;
int b = 2;
int c = 3;
int d = 1;
if(a+b > c +d)
System.out.println("a+b is greater than c+d");
a = 6
if(a+b > c +d)
System.out.println("a+b is greater than c+d");
if ( a + b > c + d )
    System.out.println("a+b is greater than c+d");
int angle1 = 20;
int angle2 = 60;
int angle3 = 50;
if(angle1 + angle2 + angle3 == 180)
    System.out.println("Valid Triangle");
angle3 += 50
angle3
angle1
angle2
if(angle1 + angle2 + angle3 == 180)
    System.out.println("Valid Triangle");
int number = 10;
number % 2
9 % 2
8 % 2
if (number % 2 == 0)
System.out.println("number is even");
if (number % 2 == 0)
System.out.println("number is even");
number = 9
if (number % 2 == 0)
System.out.println("number is even");
i > 5
i = 5
i == 5
i == 6
if(i==5)
System.out.println("i is odd");
if(i==5)
System.out.println("i is odd");
 System.out.println("i is prime");
i == 6
i = 6
if(i==5)
System.out.println("i is odd");
 System.out.println("i is prime");
if(i==5) {
System.out.println("i is odd");
System.out.println("i is prime");
}
if(i==5) {
System.out.println("i is prime");
}
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
i = i + 1
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
i = i + 1
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", 5, i, 5*i).println();
}
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", 6, i, 6*i).println();
}
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", 7, i, 7*i).println();
}
int table = 7;
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", table, i, table*i).println();
}
table = 8
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", table, i, table*i).println();
}
table = 8
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", table, i, table*i).println();
}
table = 9
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", table, i, table*i).println();
}
for(i =1; i<=10; i++) {
   System.out.printf("%d", i).println();
}
for(i=10; i<=1  ;i--) {
   System.out.printf("%d", i).println();
}
for(i=10; i>=1  ;i--) {
   System.out.printf("%d", i).println();
}
for(i=10; i>=1  ;i = i - 2) {
   System.out.printf("%d", i).println();
}
for(i=9; i>=1  ;i = i - 2) {
   System.out.printf("%d", i).println();
}
for(i =1; i<=10; i++) {
   System.out.printf("%d", i * i).println();
}
for(i =2; i<=10; i = i + 2) {
   System.out.printf("%d", i * i).println();
}
for(i =2; i<=20; i = i + 2) {
   System.out.printf("%d", i * i).println();
}
for(i =1; i<=10; i++) {
   System.out.printf("%d", (2 * i) * (2 * i) ).println();
}
for(i =1; i<=20; i = i + 2) {
   System.out.printf("%d", i * i).println();
}
int i = 1;
for ( ;i<=10 ;i++ );
i
for (i=1 ;i<=10 ;i++ );
int j;
for (i=1, j=2 ;i<=10 ;i++, j++ );
i
j
for (i=1, j=2 ;i<=10 ;i++, j--);
i
j
for(;;);
for(int i=1; i<=10; i++) {
System.out.println("No 1");
System.out.println("No 2");
}
for(int i=1; i<=10; i++) {
System.out.println("No 1");
System.out.println("No 2");
}
   System.out.println("i is less than 5");
```

## 02-IntroductionToMethods-MultiplicationTable

## Steps
- Step 00 - Section 02 - Methods - An Introduction
- Step 01 - Your First Java Method - Hello World Twice and Exercise Statements
- Step 02 - Introduction to Java Methods - Exercises and Puzzles
- Step 03 - Programming Tip - Editing Methods with JShell
- Step 04 - Introduction to Java Methods - Arguments and Parameters
- Step 05 - Introduction to Java Method Arguments - Exercises
- Step 06 - Introduction to Java Method Arguments - Puzzles and Tips
- Step 07 - Getting back to Multiplication Table - Creating a method
- Step 08 - Print Multiplication Table with a Parameter and Method Overloading
- Step 09 - Passing Multiple Parameters to a Java Method
- Step 10 - Returning from a Java Method - An Introduction
- Step 11 - Returning from a Java Method - Exercises
- Step 99 - Methods - Section Review

## Exercises

#### Methods - Basics
- Write and execute a method named ```sayHelloWorldThrice``` to print ```Hello World``` thrice.
- Write and execute a method that prints the following four statements:
   - ```I've created my first variable```
   - ```I've created my first loop```
   - ```I've created my first method```
   - ```I'm excited to learn Java```  

### Method Parameters
1. Write a method ```printNumbers(int n)``` that prints all successive integers from ```1``` to ```n```.
2. Write a method ```printSquaresOfNumbers(int n)``` that prints the squares of all successive integers from ```1``` to ```n```.

### Return value from Methods
1. Write a method that returns the sum of three integers.
2. Write a method that takes as input two integers representing two angles of a triangle, and computes the third angle. *Hint: The sum of the three angles of a triangle is 180 degrees*. 

## Code Snippets

```java
3 * 4
$2
$2 * 3
for( i =1; i<=10; i++) {
System.out.printf("%d * %d = %d", table, i, table*i).println();
}
for( i =1; i<=10; i++) {
    System.out.printf("%d * %d = %d", table, i, table*i).println();
}
for( i =1; i<=10; i++) {
    System.out.printf("%d * %d = %d", table, i, table*i).println();
}
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", table, i, table*i).println();
}
int table = 7;
for( i =1; i<=10; i++) {
System.out.printf("%d * %d = %d", table, i, table*i).println();
}
table = 8
for( i =1; i<=10; i++) {
System.out.printf("%d * %d = %d", table, i, table*i).println();
}
System.out.println("Hello World")
System.out.println("Hello World")
System.out.println("Hello World")
System.out.println("Hello World");
 System.out.println("Hello World");
System.out.println("Hello World");
 System.out.println("Hello World");
sayHelloWorldTwice()
sayHelloWorldTwice()
void sayHelloWorldThrice(){
 System.out.println("Hello World");
 System.out.println("Hello World");
 System.out.println("Hello World");
}
sayHelloWorldThrice()
printLearningExperience()
printLearningExperience()
void NameOfMethod(){
}
void nameOfMethod(){
}
void sayHelloWorldTwice(){
   System.out.println("HelloWorld");
   System.out.println("HelloWorld");
}
sayHelloWorldTwice()
void printLearningExperience() {
System.out.println("I've created sdf first variable");
System.out.println("I've created fsadjf first method");
System.out.println("I've created fsajdfl first loop");
System.out.println("I'm excited fasdflkjfskfsd learn Java");
}
printLearningExperience()
sayHelloWorldThrice()
sayHelloWorldTwice()
sayHelloWorld(1)
sayHelloWorld(1)
sayHelloWorld(2)
sayHelloWorld(2)
sayHelloWorld(4)
sayHelloWorld(6)
void sayHelloWorld(int noOfTimes) {
	for(int i=1; i<=noOfTimes; i++) {
		System.out.println("Hello World");
	}
}
sayHelloWorld(6)
sayHelloWorld(3)
sayHelloWorld(2)
void printNumbers(int n) {
    for(int i=1; i<=n; i++) {
	    System.out.println(i);
    }
}
printNumbers(10)
printNumbers(3)
void printSquaresOfNumbers(int n) {
    for(int i=1; i<=n; i++) {
         System.out.println(i*i);
    }
}
printSquaresOfNumbers(5)
printSquaresOfNumbers(3)
sayHelloWorld(4)
for( i =1; i<=10; i++) {
	System.out.printf("%d * %d = %d", table, i, table*i).println();
}
int i;
for(i=1;i<=10;i++)
    System.out.printf("%d * %d = %d", 5, i, 5 * i).println();
for(i=1;i<=10;i++) {
    System.out.printf("%d * %d = %d", 5, i, 5 * i).println();
}
void printMultiplicationTable() {
	for(int i=1;i<=10;i++) {
		System.out.printf("%d * %d = %d", 5, i, 5 * i).println();
	}
}
printMultiplicationTable()

void printMultiplicationTable(int table) {
	for(int i=1;i<=10;i++) {
		System.out.printf("%d * %d = %d", table, i, table * i).println();
	}
}

printMultiplicationTable(6)
printMultiplicationTable(7)
printMultiplicationTable()
printMultiplicationTable(6)
Math.max(1,2)
void sum(int firstNumber,int secondNumber) {
     int sum = firstNumber + secondNumber;
     System.out.println(sum);
}
sum(5, 10)
void sum(int firstNumber,int secondNumber, int thirdNumber) {
     int sum = firstNumber + secondNumber + thirdNumber;
     System.out.println(sum);
}
sum(5, 10, 15)
Math.max(4,5)
$110
int max = Math.max(15, 25);
max
sum(1, 10)
int sumOfTwoNumbers(int firstNumber, int secondNumber) {
    int sum = firstNumber + secondNumber;
    return sum;
}
sumOfTwoNumbers(1,1)
int sum = sumOfThreeNumbers(2,3,4);
calculateThirdAngle(20, 50)
int sumOfThreeNumbers(int firstNumber, int secondNumber, int thirdNumber) {
      int sum = firstNumber + secondNumber + thirdNumber;
      return sum;
}
sumOfThreeNumbers(1,2,3)
sumOfThreeNumbers(15,2,3)
int calculateThirdAngle(int angle1, int angle2) {
       int angle3 = 180 - (angle1 + angle2);
       return angle3;
}
calculateThirdAngle(20, 20)
calculateThirdAngle(20, 20)
```


### 03-IntroductionToJavaPlatform

## Steps
- Step 00 - Section 03 - Overview Of Java Platform - Section Overview
- Step 01 - Overview Of Java Platform - An Introduction - java, javac, bytecode and JVM
- Step 02 - Java Class and Object - First Look
- Step 03 - Create a method in a Java class
- Step 04 - Create and Compile Planet.java class
- Step 05 - Run Planet calss with Java - Using a main method
- Step 06 - Play and Learn with Planet Class
- Step 07 - JDK vs JRE vs JVM

## Code Snippets (Including Output)

```java
jshell> System.out.println("I love JShell");
I love JShell

jshell> class Country {
   ...> }
|  created class Country

jshell> Country india = new Country()
india ==> Country@6e06451e

jshell> Country usa = new Country()
usa ==> Country@6e1567f1

jshell> class Planet {
   ...> }
|  created class Planet

jshell> Planet planet = new Planet()
planet ==> Planet@56ef9176

jshell> Planet earth = new Planet()
earth ==> Planet@1ed4004b

jshell> Planet venus = new Planet()
venus ==> Planet@25bbe1b6

jshell> void printMultiplicationTable() {
   ...>     for(int i=1;i<=10;i++) {
   ...>         System.out.printf("%d * %d = %d", 5, i, 5 * i).println();
   ...>     }
   ...> }
|  created method printMultiplicationTable()

jshell> void printMultiplicationTable(int table) {
   ...>     for(int i=1;i<=10;i++) {
   ...>         System.out.printf("%d * %d = %d", table, i, table * i).println();
   ...>     }
   ...> }
|  created method printMultiplicationTable(int)

jshell> 
 
jshell> /methods
|    void |    void printMultiplicationTable()
|    void printMultiplicationTable(int)

jshell>  
jshell> class Planet {
   ...> }
|  modified class Planet

jshell> Planet earth = new Planet()
earth ==> Planet@73846619

jshell> Planet venus = new Planet()
venus ==> Planet@4bec1f0c

jshell> class Planet {
   ...>      void revolve() {
   ...>           System.out.println("Revolve");
   ...>      }
   ...> }
|  replaced class Planet
|    update replaced variable planet, reset to null
|    update replaced variable earth, reset to null
|    update replaced variable venus, reset to null

jshell> Planet earth = new Planet()
earth ==> Planet@192b07fd

jshell> Planet venus = new Planet()
venus ==> Planet@64bfbc86

jshell> Planet.revolve()
|  Error:
|  non-static method revolve() cannot be referenced from a static context
|  Planet.revolve()
|  ^------------^

jshell> earth.revolve()
Revolve

jshell> venus.revolve()
Revolve

jshell> class Country {
   ...>    void comingSoon() {
   ...>       System.out.println("Coming Soon");
   ...>    }
   ...> }
|  replaced class Country
|    update replaced variable country, reset to null
|    update replaced variable india, reset to null
|    update replaced variable usa, reset to null

jshell> Country india = new Country()
india ==> Country@60c6f5b

jshell> Country netherlands = new Country()
netherlands ==> Country@3c0f93f1

jshell> india.comingSoon()
Coming Soon

jshell> netherlands.comingSoon()
Coming Soon

jshell> /list Country

  27 : class Country {
          void comingSoon() {
             System.out.println("Coming Soon");
          }
       }

jshell> /list Planet

  22 : class Planet {
            void revolve() {
                 System.out.println("Revolve");
            }
       }

jshell> 
```


### /03-IntroductionToJavaPlatform/Planet.java

```java
class Planet {

    void revolve() {
         System.out.println("Revolve");
    }

    public static void main(String[] args) {
    	Planet earth = new Planet();
    	earth.revolve();
    }
}
```

## 04-IntroductionToEclipse-FirstJavaProject

## Steps
- Step 00 - Intro to Section and Installing Eclipse
- Step 01 - Creating a New Java Project with Eclipse
- Step 02 - Your first Java class with Eclipse
- Step 03 - Writing Multiplication Table Java Program with Eclipse
- Step 04 - Adding more methods for Multiplication Table Program
- Step 05 - Programming Tip 1 : Refactoring with Eclipse
- Step 06 - Programming Tip 2 : Debugging with Eclipse
- Step 07 - Programming Tip 3 : Eclipse vs JShell - How to choose?

## Code Examples

### /04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/HelloWorld.java

```java
package com.in28minutes.firstjavaproject;

public class HelloWorld {

	public static void main(String[] args) {
		
	}

}
```


### /04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/KeyboardShortcuts.java

```java
package com.in28minutes.firstjavaproject;

public class KeyboardShortcuts {
	public static void main(String[] args) {
		int i = 0;
		System.out.println(i);
	}
}
```


### /04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/MultiplicationTable.java

```java
package com.in28minutes.firstjavaproject;

public class MultiplicationTable {
	
	void print() {
		print(5);
	}
	
	void print(int table) {
		print(table, 1, 10);
	}
	
	void print(int table, int from, int to) {
		for (int i = from; i <= to; i++) {
			System.out.printf("%d X %d = %d", table, i, table * i).println();
		}
	}
}
```


### /04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/MultiplicationTableRunner.java

```java
package com.in28minutes.firstjavaproject;

public class MultiplicationTableRunner {

	public static void main(String[] args) {
		MultiplicationTable table = new MultiplicationTable();
		table.print();
		
		//table.print(6);
		//table.print(6, 11, 20);
	}

}
```


### /04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/MutliplicationTableBeforeRefactoring.java

```java
package com.in28minutes.firstjavaproject;

public class MutliplicationTableBeforeRefactoring {
	void print() {
		for (int i = 1; i <= 10; i++) {
			System.out.printf("%d X %d = %d", 5, i, 5 * i).println();
		}
	}

	void print(int table) {
		for (int i = 1; i <= 10; i++) {
			System.out.printf("%d X %d = %d", table, i, table * i).println();
		}
	}

	void print(int table, int from, int to) {
		for (int i = from; i <= to; i++) {
			System.out.printf("%d X %d = %d", table, i, table * i).println();
		}
	}
}
```


## 05-IntroductionToObjectOrientedProgramming

## Steps
- Step 00 - Introduction to Object Oriented Programming - Section Overview
- Step 01 - Introduction to Object Oriented Programming - Basics
- Step 02 - Introduction to Object Oriented Programming - Terminology - Class, Object, State and Behavior
- Step 03 - Introduction to Object Oriented Programming - Exercise - Online Shopping System and Person
- Step 04 - Create Motor Bike Java Class and a couple of objects
- Step 05 - Exercise Solutions - Book class and Three instances
- Step 06 - Introducing State of an object with speed variable
- Step 07 - Understanding basics of Encapsulation with Setter methods
- Step 08 - Exercises and Tips - Getters and Generating Getters and Setters with Eclipse
- Step 09 - Puzzles on this and initialization of member variables
- Step 10 - First Advantage of Encapsulation
- Step 11 - Introduction to Encapsulation - Level 2
- Step 12 - Encapsulation Exercises - Better Validation and Book class
- Step 13 - Introdcution to Abstraction
- Step 14 - Introduction to Java Constructors
- Step 15 - Introduction to Java Constructors - Exercises and Puzzles
- Step 16 - Introduction to Object Oriented Programming - Conclusion

## Exercises
- In each of the following systems, identify the basic entities involved, and organize them using object oriented terminology:
     - Online Shopping System
     - Person
- Provide Better Encapsulation and Validation for Book and MotorBike class
- Create a constructor for Book class and create three instances

## Code Examples

### /05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/Book.java

```java
package com.in28minutes.oops;

public class Book {
	
	private int noOfCopies;

	public Book(int noOfCopies) {
		this.noOfCopies = noOfCopies;
	}

	public void setNoOfCopies(int noOfCopies) {
		if (noOfCopies > 0)
			this.noOfCopies = noOfCopies;
	}

	public void increaseNoOfCopies(int howMuch) {
		setNoOfCopies(this.noOfCopies + howMuch);
	}

	public void decreaseNoOfCopies(int howMuch) {
		setNoOfCopies(this.noOfCopies - howMuch);
	}

}
```


### /05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/BookRunner.java

```java
package com.in28minutes.oops;

public class BookRunner {

	public static void main(String[] args) {
		// Create a new class called Book 
		// Create three instances
		Book artOfComputerProgramming = new Book(100);
		Book effectiveJava = new Book(50);
		Book cleanCode = new Book(40);
		
		artOfComputerProgramming.setNoOfCopies(100);
		effectiveJava.setNoOfCopies(50);
		cleanCode.setNoOfCopies(45);
	}

}
```


### /05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/MotorBike.java

```java
package com.in28minutes.oops;

public class MotorBike {
	//state
	private int speed; //member variable
	

	//constructors
	MotorBike() {
		this(5);
	}
	
	MotorBike(int speed) {
		this.speed = speed;
	}
	
	//behavior
	public int getSpeed() {
		return speed;
	}

	public void setSpeed(int speed) {
		if(speed > 0 )
			this.speed = speed;
	}

	public void increaseSpeed(int howMuch) {
		setSpeed(this.speed + howMuch);
	}

	public void decreaseSpeed(int howMuch) {
		setSpeed(this.speed - howMuch);
	}
	
	void start() {
		System.out.println("Bike Started");
	}
}
```


### /05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/MotorBikeRunner.java

```java
package com.in28minutes.oops;

public class MotorBikeRunner {

	public static void main(String[] args) {
		
		MotorBike ducati = new MotorBike(100);
		
		MotorBike honda = new MotorBike(200);
		
		MotorBike somethingElse = new MotorBike();
		
		System.out.println(ducati.getSpeed());
		
		System.out.println(honda.getSpeed());
		
		System.out.println(somethingElse.getSpeed());

		
		ducati.start();

		honda.start();
		
		//ducati.setSpeed(100);
		
		ducati.increaseSpeed(100);
				
		honda.increaseSpeed(100);
		
		ducati.decreaseSpeed(250);
		
		honda.decreaseSpeed(250);
		
		System.out.println(ducati.getSpeed());
		
		System.out.println(honda.getSpeed());
	}

}

// Create a new class called Book 
// Create three instances
// Art Of Computer Programming
// Effective Java
// Clean Code
```

### /05-IntroductionToObjectOrientedProgramming/entireoutput-constructor-puzzles.txt

```java
Last login: Mon Jan 29 10:33:44 on ttys000
Rangas-MacBook-Pro:~ rangaraokaranam$ jshell
|  Welcome to JShell -- Version 9.0.1
|  For an introduction type: /help intro

jshell> class Cart {
   ...> };
|  created class Cart

jshell> Cart cart1 = new Cart();
cart1 ==> Cart@3f49dace

jshell> class Cart {
   ...>     Cart() {
   ...>     }
   ...> };
|  replaced class Cart
|    update replaced variable cart1, reset to null

jshell> Cart cart1 = new Cart();
cart1 ==> Cart@59494225

jshell> class Cart {
   ...>     Cart() {
   ...>         System.out.println("Constructor is called");
   ...>     }
   ...> }
|  modified class Cart

jshell> Cart cart1 = new Cart();
Constructor is called
cart1 ==> Cart@6e1567f1

jshell> 
```


#  06-PrimitiveDataTypesAndAlternatives

## Steps
- Step 00 - Primitive Data Types in Depth - Section Overview
- Step 01 - Basics about Java Integer Data Types - Casting, Operators and More
- Step 02 - Java Integer Data Types - Puzzles - Octal, Hexadecimal, Post and Pre increment
- Step 03 - Java Integer Data Types - Exercises - BiNumber - add, multiply and double
- Step 04 - Java Floating Point Data Types - Casting , Conversion and Accuracy
- Step 05 - Introduction to BigDecimal Java Class
- Step 06 - BigDecimal Puzzles - Adding Integers
- Step 07 - BigDecimal Exercises - Simple Interest Calculation
- Step 08 - Java Boolean Data Type - Relational and Logical Operators
- Step 09 - Java Boolean Data Type - Puzzles - Short Circuit Operators
- Step 10 - Java Character Data Type char - Representation and Conversion
- Step 11 - Java char Data Type - Exercises 1 - isVowel
- Step 12 - Java char Data Type - Exercises 2 - isDigit
- Step 13 - Java char Data Type - Exercises 3 - isConsonant, List Upper Case and Lower Case Characters
- Step 14 - Primitive Data Types in Depth - Conclusion

## Exercises

#### Big Decimal

- Calculate formula for Simple Interest Formula
   - Total Amount = principal + principal * interest * noOfYears;

```java
 SimpleInterestCalculator calculator = 
        new SimpleInterestCalculator("4500.00", "7.5");
 BigDecimal totalValue = 
        calculator.calculateTotalValue(5);// 5 years
 System.out.println(totalSum);
```

#### char data type

Implement MyChar class

```java
MyChar myChar = new MyChar('c');
System.out.println(myChar.isVowel());
        //'a', 'e', 'i', 'o', 'u' and Capitals
System.out.println(myChar.isDigit());
System.out.println(myChar.isAlphabet());
MyChar.printLowerCaseAlphabets();
MyChar.printUpperCaseAlphabets();
```

## Code Examples

### /06-PrimitiveDataTypesAndAlternatives/commands.txt

```java
Byte.SIZE
Byte.BYTES
Byte.MAX_VALUE
Byte.MIN_VALUE
Short.BYTES
Integer.BYTES
Long.BYTES
Integer.MAX_VALUE
Short.MAX_VALUE
Byte.SIZE
Byte.MIN_VALUE
Byte.MAX_VALUE
Short.BYTES
Integer.BYTES
Long.BYTES
Integer.MAX_VALUE
byte c = 13;
long l = 50000000000l;
i = (int) l
l = i
int eight = 010;
int sixteen = 0x10;
int fifteen = 0XF;
int big = 0XBBAACC;
Short.MAX_VALUE
short s = (short) i;
int i1 = s;
i
i
i
i
34.5
34.56789
double dbl = 34.5678;
float f2 = (float)dbl;
dbl++
dbl--
dbl % 5
float f = i;
34.56789876 + 34.2234
number1.add(number2);
number1
BigDecimal number3 = number1.add(number2);
number1
BigDecimal number1 = new BigDecimal("34.56789876");
BigDecimal number10 = new BigDecimal(34.2234);
BigDecimal number11 = new BigDecimal("34.56789876");
number10.add(number11)
number10.multiply(number11)
BigDecimal number = new BigDecimal("11.5");
BigDecimal number2 = new BigDecimal("23.45678");
number.add(number2)
number.add(new BigDecimal(i))
number.multiply(new BigDecimal(i))
number.divide(new BigDecimal(100))
number.divide(new BigDecimal("100.01234"))
number.divide(new BigDecimal("100.012"))
number.divide(new BigDecimal("100.12"))
number.divide(new BigDecimal("100.1"))
number.divide(new BigDecimal("1001"))
number.divide(new BigDecimal("100"))
boolean isValue = false;
i > 7
i >= 7
i < 7
i <= 7
i == 6
i == 7
i == 8
i = 8
i = 7
i == 7
i > 15
i >= 15
i <= 25
i >= 15 && i <= 25
i = 30
i >= 15 && i <= 25
i = 5
i >= 15 && i <= 25
true && true
true && false
false && true
false && false
false || true
false || true
true || false
true || true
false || false
false ^ false
false ^ true
true ^ false
true ^ true
!true
!false
int x = 6;
!(x>7)
!(x>7)
true || ++i==11
i
int i = 10;
int j = 15;
j > 15 && i++ > 5
j
i
j > 15 & i++ > 5
j
i
i++;
i++;
char ch2 = '\u0022';
char ch3 = '\u00A2';
ch++
ch
++ch
++ch
ch + 5
ch
(int)ch
ch
System.out.println(ch);
char ch = '\t';
System.out.println(ch);
System.out.println(ch);
(int)'1'
(int)'0'
(int)'9'
(int)'2'
(int)'a'
(int)'z'
(int)'A'
(int)'Z'
		for (char ch = 'A'; ch <= 'Z'; ch++) {
			System.out.println(ch);

}
		for (char ch = 'A'; ch <= 'Z'; ch++) {
			System.out.println(ch);
}
		for (char ch = 'A'; ch <= 'C'; ch++) {
			System.out.println(ch);
}
```


### /06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/BiNumber.java

```java
package com.in28minutes.primitive.datatypes;

public class BiNumber {
	private int number1;
	private int number2;

	public int getNumber1() {
		return number1;
	}

	public void setNumber1(int number1) {
		this.number1 = number1;
	}

	public int getNumber2() {
		return number2;
	}

	public void setNumber2(int number2) {
		this.number2 = number2;
	}

	public BiNumber(int number1, int number2) {
		this.number1 = number1;
		this.number2 = number2;
	}

	public int add() {
		return number1 + number2;
	}

	public int multiply() {
		return number1 * number2;
	}

	public void doubleValue() {
		this.number1 *= 2;
		this.number2 *= 2;
	}
}
```


### /06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/BiNumberRunner.java

```java
package com.in28minutes.primitive.datatypes;

public class BiNumberRunner {

	public static void main(String[] args) {
		BiNumber numbers = new BiNumber(2, 3);
		
		System.out.println(numbers.add());//2+3
		System.out.println(numbers.multiply());//2*3
		
		numbers.doubleValue();//Double both numbers 
		
		System.out.println(numbers.getNumber1());//4
		System.out.println(numbers.getNumber2());//6
	}

}
```


### /06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/MyChar.java

```java
package com.in28minutes.primitive.datatypes;

public class MyChar {

	private char ch;

	public MyChar(char ch) {
		this.ch = ch;
	}

	public boolean isVowel() {
		//'a' e i o u or A E I O U
		if(ch == 'a' || ch == 'A')
			return true;

		if(ch == 'e' || ch == 'E')
			return true;
		
		if(ch == 'i' || ch == 'E')
			return true;
		
		if(ch == 'o' || ch == 'O')
			return true;
		
		if(ch == 'u' || ch == 'U')
			return true;
		
		return false;
	}

	public boolean isDigit() {
		if(ch >= 48 && ch <=57) //between '0' and '9'  
		  return true;
		
		return false;
	}

	public boolean isAlphabet() {
		if(ch >= 97 && ch <=122) //between 'a' and 'z'  
		  return true;

		if(ch >= 65 && ch <=90) //between 'A' and 'Z'  
			  return true;

		return false;
	}

	public boolean isConsonant() {
		//Alphabet and it is not VOWEL
		//! [a , e, i ,o , u]
		if(isAlphabet() && !isVowel()) 
			return true;
		
		return false;
		
	}

	public static void printLowerCaseAlphabets() {
		//'a' to 'z'
		for (char ch = 'a'; ch <= 'z'; ch++) {
			System.out.println(ch);
		}
	}

	public static void printUpperCaseAlphabets() {
		for (char ch = 'A'; ch <= 'Z'; ch++) {
			System.out.println(ch);
		}
		
	}
}
```


### /06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/MyCharRunner.java

```java
package com.in28minutes.primitive.datatypes;

public class MyCharRunner {

	public static void main(String[] args) {
		MyChar myChar = new MyChar('B');
		System.out.println(myChar.isVowel());
		
		//'a', 'e', 'i', 'o', 'u' and Capitals
		System.out.println(myChar.isDigit());
		System.out.println(myChar.isAlphabet()); //'a' to 'z' or 'A' to 'Z'

		System.out.println(myChar.isConsonant());
		
		MyChar.printLowerCaseAlphabets();
		MyChar.printUpperCaseAlphabets();
	}

}
```


### /06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/SimpleInterestCalculator.java

```java
package com.in28minutes.primitive.datatypes;

import java.math.BigDecimal;

public class SimpleInterestCalculator {

	BigDecimal principal;

	BigDecimal interest;

	public SimpleInterestCalculator(String principal, String interest) {
		this.principal = new BigDecimal(principal);
		this.interest = new BigDecimal(interest).divide(new BigDecimal(100));
	}

	public BigDecimal calculateTotalValue(int noOfYears) {
		// Total Value = principal + principal * interest * noOfYears;
		BigDecimal noOfYearsBigDecimal = new BigDecimal(noOfYears);
		BigDecimal totalValue = principal.add(principal.multiply(interest).multiply(noOfYearsBigDecimal));
		return totalValue;
	}

}
```


### /06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/SimpleInterestCalculatorRunner.java

```java
package com.in28minutes.primitive.datatypes;

import java.math.BigDecimal;

public class SimpleInterestCalculatorRunner {

	public static void main(String[] args) {

		SimpleInterestCalculator calculator = 
		        new SimpleInterestCalculator("4500.00", "7.5");
		 BigDecimal totalValue = 
		        calculator.calculateTotalValue(5);// 5 years
		 //6187.50000
		 System.out.println(totalValue);
	}

}
```


# 07-Conditionals

## Steps
- Step 00 - Conditionals with Java - Section Overview
- Step 01 - Introduction to If Else Statement
- Step 02 - Introduction to Nested If Else
- Step 03 - If Else Statement - Puzzles
- Step 04 - If Else Problem - How to get User Input in Java?
- Step 05 - If Else Problem - How to get number 2 and choice from user?
- Step 06 - If Else Problem - Implementing with Nested If Else
- Step 07 - Java Switch Statement - An introduction
- Step 08 - Java Switch Statement - Puzzles - Default, Break and Fall Through
- Step 09 - Java Switch Statement - Exercises - isWeekDay, nameOfMonth, nameOfDay
- Step 10 - Java Ternary Operation - An Introduction
- Step 11 - Conditionals with Java - Conclusion

## Exercises

#### If and Nested If Else - Design a Menu
- Ask User for input
  - Enter two numbers 
  - Choose an Operation
      - add
      - multiply
      - divide 
      - subtract
      - ...
  - Publish Result

```
Enter Number1: 
2

Enter Number2: 
4

1 - Add
2 - Subtract
3 - Divide
4 - Multiply
Choose Operation: 4

Result is - 8
```

#### Switch 
- ```public static boolean isWeekDay(int dayNumber) {``` 
  - input - number of day 0 (Sunday) to 6(Saturday)
  - return if the day is a Week Day.   
- ```public static String determineNameOfMonth(int monthNumber) {```
  - input - number of month 1(January) to 12(December)
  - output - Name of month
- ```public static String determineNameOfDay(int dayNumber) {```
  - input - number of day 0 (Sunday) to 6(Saturday)
  - Return the day of week in text


## Code Examples

### /07-Conditionals/commands.txt

```java
if(true) {
   System.out.println("True");
}
if(false) {
   System.out.println("True");
}
if(i==3) {
   System.out.println("True");
}
if(i<2) {
    System.out.println("True");
}
if(i<=3 || i>=35) {
    System.out.println("True");
}
if(i<=3 && i>=35) {
    System.out.println("True");
}
if (i==3) {
   System.out.println("True");
} else {
   System.out.println("i is not 3");
}
i = 5
if (i==3) {
   System.out.println("True");
} else {
   System.out.println("i is not 3");
}
if(i==1) {
   System.out.println("i");
}
switch (i) {
   case 1 : System.out.println("1");
   case 5 : System.out.println("5");
   default : System.out.println("default");
}
i = 1
switch (i) {
   case 1 : System.out.println("1");
   case 5 : System.out.println("5");
   default : System.out.println("default");
}
switch (i) {
   case 1 : System.out.println("1"); break;
   case 5 : System.out.println("5"); break;
   default : System.out.println("default"); break;
}
boolean isEven;
int i =5;
if(i%2==0) {
  isEven = true;
} else {
  isEven = false;
}
isEven
i = 6
if(i%2==0) {
  isEven = false;
}
if(i%2==0) {
  isEven = true;
} else {
  isEven = false;
}
isEven
isEven = ( i%2==0 ? true : false  )
i = 6
isEven = ( i%2==0 ? true : false  )
i = 7
isEven = ( i%2==0 ? true : false  )
i = 6
String even = ( i%2 ==0 ? "YES" : "NO" );
```


### /07-Conditionals/src/com/in28minutes/ifstatement/examples/IfStatementRunner.java

```java
package com.in28minutes.ifstatement.examples;

public class IfStatementRunner {

	public static void main(String[] args) {
		puzzle5();
	}

	private static void puzzle1() {
		int k = 15;
		if (k > 20) {
			System.out.println(1);
		} else if (k > 10) {
			System.out.println(2);
		} else if (k < 20) {
			System.out.println(3);
		} else {
			System.out.println(4);
		}
		
	}

	private static void puzzle2() {
		int l = 15;

		if (l < 20)
			System.out.println("l<20");//
		if (l > 20)
			System.out.println("l>20");
		else
			System.out.println("Who am I?");//
	}

	
	
	private static void puzzle3() {
		int m = 15;

		if(m>20) 
		    if(m<20)
		System.out.println("m>20");
		    else
		System.out.println("Who am I?");
	}


	private static void puzzle5() {
		int number = 5;
		if(number < 0) 
		    number = number + 10; 
		number++; 
		System.out.println(number);
	}

	private static void basicNestedIfElse() {
		int i = 24;
		// i is 25
		// i is 24
		// i is neither 25 or 24
		if (i == 25) {
			System.out.println("i = 25");
		} else if (i == 24) {
			System.out.println("i = 24");
		} else if (i == 23) {
			System.out.println("i = 23");
		} else {
			System.out.println("i != 24 and i !=25 and i !=23");
		}
	}

}
```


### /07-Conditionals/src/com/in28minutes/ifstatement/examples/MenuRunner.java

```java
package com.in28minutes.ifstatement.examples;

import java.util.Scanner;

public class MenuRunner {
	public static void main(String[] args) {
		// Type obj = new Type(argument);
		Scanner scanner = new Scanner(System.in);
		System.out.print("Enter Number1: ");
		int number1 = scanner.nextInt();

		System.out.print("Enter Number2: ");
		int number2 = scanner.nextInt();

		System.out.println("Choices Available are ");
		System.out.println("1 - Add");
		System.out.println("2 - Subtract");
		System.out.println("3 - Divide");
		System.out.println("4 - Multiply");

		System.out.print("Enter Choice: ");
		int choice = scanner.nextInt();

		System.out.println("Your Choices are");
		System.out.println("Number1 " + number1);
		System.out.println("Number2 " + number2);
		System.out.println("Choice " + choice);

		performOperationUsingSwitch(number1, number2, choice);
	}

	private static void performOperationUsingNestedIfElse(int number1, int number2, int choice) {
		if (choice == 1) {
			System.out.println("Result " + (number1 + number2));
		} else if (choice == 2) {
			System.out.println("Result " + (number1 - number2));
		} else if (choice == 3) {
			System.out.println("Result " + (number1 / number2));
		} else if (choice == 4) {
			System.out.println("Result " + (number1 * number2));
		} else {
			System.out.println("Invalid Operation");
		}
	}

	private static void performOperationUsingSwitch(int number1, int number2, int choice) {
		switch (choice) {
		case 1:
			System.out.println("Result " + (number1 + number2));
			break;
		case 2:
			System.out.println("Result " + (number1 - number2));
			break;
		case 3:
			System.out.println("Result " + (number1 / number2));
			break;
		case 4:
			System.out.println("Result " + (number1 * number2));
			break;
		default:
			System.out.println("Invalid Operation");
			break;
		}

	}

}
```


### /07-Conditionals/src/com/in28minutes/ifstatement/examples/SwitchExercisesRunner.java

```java
package com.in28minutes.ifstatement.examples;

public class SwitchExercisesRunner {

	public static void main(String[] args) {
		System.out.println(isWeekDay(5));
	}

	public static boolean isWeekDay(int dayNumber) {
		switch(dayNumber) {
		//case 0 :
		//case 6 : return false;
		case 1 : 
		case 2 :
		case 3 :
		case 4 :
		case 5 : return true;
		}

		return false;
	}
	
	public static String determineNameOfDay(int dayNumber) {
		switch (dayNumber) {
		case 0:
			return "Sunday";
		case 1:
			return "Monday";
		case 2:
			return "Tuesday";
		case 3:
			return "Wednesday";
		case 4:
			return "Thursday";
		case 5:
			return "Friday";
		case 6:
			return "Saturday";
		}

		return "Invalid_day";
	}
}
```


### /07-Conditionals/src/com/in28minutes/ifstatement/examples/SwitchStatementRunner.java

```java
package com.in28minutes.ifstatement.examples;

public class SwitchStatementRunner {
	public static void main(String[] args) {
		puzzle4();
	}

	private static void puzzle1() {
		int number = 2;
		switch (number) {
		case 1:
			System.out.println(1);
		case 2:
			System.out.println(2);
		case 3:
			System.out.println(3);
		default:
			System.out.println("Default");
		}
	}

	private static void puzzle2() {
		int number = 2;
		switch (number) {
		case 1:
			System.out.println(1);
			break;
		case 2:
		case 3:
			System.out.println("Number is 2 or 3");
			break;
		default:
			System.out.println("Default");
			break;
		}
	}

	private static void puzzle3() {
		int number = 10;
		switch (number) {
		case 1:
			System.out.println(1);
			break;
		case 2:
			System.out.println(2);
			break;
		case 3:
			System.out.println(3);
			break;
		default:
			System.out.println("Default");
			break;
		}
	}

	private static void puzzle4() {
		int number = 10;
		switch (number) {
		default:
			System.out.println("Default");
			break;
		case 1:
			System.out.println(1);
			break;
		case 2:
			System.out.println(2);
			break;
		case 3:
			System.out.println(3);
			break;
		}
	}

	private static void puzzle5() {
		long l = 15;
		/*switch(l){
		
		}*/
	}

	private static void puzzle6() {
		int number = 10;
		int i = number * 2;
		switch (number) {
		 //case number>5: System.out.println("number>5");
		}
	}

}
```

# 08-Loops

## Steps
- Step 00 - Java Loops - Section Introduction
- Step 01 - Java For Loop - Syntax and Puzzles
- Step 02 - Java For Loop - Exercises Overview and First Exercise Prime Numbers
- Step 03 - Java For Loop - Exercise - Sum Upto N Numbers and Sum of Divisors
- Step 04 - Java For Loop - Exercise - Print a Number Triangle
- Step 05 - While Loop in Java - An Introduction
- Step 06 - While Loop - Exericises - Cubes and Squares upto limit
- Step 07 - Do While Loop in Java - An Introduction
- Step 08 - Do While Loop in Java - An Example - Cube while user enters positive numbers
- Step 09 - Introduction to Break and Continue
- Step 10 - Selecting Loop in Java - For vs While vs Do While

## Exercises

#### For Loop

Implement MyNumber class with behavior shown in the example below:

```java
MyNumber number = new MyNumber(9);

number.isPrime(); //Is a number Prime? 
//Hint : 5 => true, 7 => true, 11 => true, 6 => false

int sum = number.sumUptoN();//Sum of numbers upto n?
//1 + 2 + 3 + 4 + 5 + 6

int sumOfDivisors = number.sumOfDivisors();

number.printANumberTriangle();
//1
//1 2
//1 2 3
//1 2 3 4 
//1 2 3 4 5
```

#### While
Implement WhileNumberPlayer class with behavior shown in the example below:

```java

WhileNumberPlayer player = new WhileNumberPlayer(30);//limit

player.printSquaresUptoLimit();
//For limit = 30, output would be 1 4 9 16 25

player.printCubesUptoLimit();
//For limit = 30, output would be 1 8 27

```

#### Choosing Loops

Thinking Exercise 
- What would we use for the Menu 
- If we would want to run the Menu again and again?
```
Enter Number1: 
2

Enter Number2: 
4

1 - Add
2 - Subtract
3 - Divide
4 - Multiply
5 - Exit

Choose Operation: 4
Result is 8

Choose Operation: 1
Result is 6

Choose Operation: 5

Thank You!

```

## Code Examples

### /08-Loops/commands.txt

```java
for (int i = 0; i<= 10; i++) {
   System.out.print (i + " ");
}
for (int i = 0; i<= 10; i = i + 2) {
   System.out.print (i + " ");
}
for (int i = 1; i<= 10; i = i + 2) {
   System.out.print (i + " ");
}
for (int i = 11; i<= 10; i = i + 2) {
   System.out.print (i + " ");
}
for (int i = 11; i<= 20;) {
   System.out.print (i + " ");
   i++;
}
for (; i<= 30;i++) {
   System.out.print (i + " ");
}
9 % 2
9 % 3
if (i>2) {
   System.out.println("i>2");
}
int i = 3;
if (i>2) {
   System.out.println("i>2");
}
i = 0
while (i <5) {
   System.out.println(i);
   i++;
}
i
i = 6
while (i < 5) {
   System.out.println(i);
   i++;
}
i = -2
while (i < 5) {
   System.out.println(i);
}
while (i < 5) {
   System.out.println(i);
   i++;
}
i
while (i < 5) {
   System.out.print(i + " ");
   i++;
}
i
i = 1
do {
   System.out.print(i + " ");
   i++;
} while (i<5);
i = 10
while (i < 5) {
   System.out.print(i + " ");
   i++;
}
do {
   System.out.print(i + " ");
   i++;
} while (i<5);
for(i=1;i<=10;i++) {
   if(i==5)
      break;
   System.out.print(i + " ");
}
for(i=1;i<=10;i++) {
   if(i%2==0)
      break;
   System.out.print(i + " ");
}
for(i=1;i<=10;i++) {
   if(i%2==0)
     continue;
   System.out.print(i + " ");
}
for(i=1;i<=10;i++) {
   if(i%2!=0)
     continue;
   System.out.print(i + " ");
}
```


### /08-Loops/src/com/in28minutes/loops/DoWhileRepeatedQuestionRunner.java

```java
package com.in28minutes.loops;

import java.util.Scanner;

public class DoWhileRepeatedQuestionRunner {

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		int number = -1;

		do {
			if (number != -1) {
				System.out.println("Cube is " + (number * number * number));
			}
			System.out.print("Enter a number: ");
			number = scanner.nextInt();
		} while (number >= 0);
		System.out.print("Thank You! Have Fun!");
	}

}
```


### /08-Loops/src/com/in28minutes/loops/MyNumber.java

```java
package com.in28minutes.loops;

public class MyNumber {

	private int number;

	public MyNumber(int number) {
		this.number = number;
	}

	public boolean isPrime() {
		// 2 to number-1
		// How can check if a number is divisible by 2?

		if (number < 2) {
			return false;
		}

		for (int i = 2; i <= number - 1; i++) {
			if (number % i == 0) {
				return false;
			}
		}

		return true;
	}

	public int sumUptoN() {
		int sum = 0;

		for (int i = 1; i <= number; i++) {
			sum = sum + i;
		}

		return sum;
	}

	public int sumOfDivisors() {
		// 6 except 1 , 6 => 2,3
		// 2 + 3 + 4 + 5

		int sum = 0;

		for (int i = 2; i <= number - 1; i++) {
			if (number % i == 0) {
				sum = sum + i;
			}
		}

		return sum;
	}

	public void printNumberTriangle() {
		// 1
		// 1 2
		// 1 2 3
		// 1 2 3 4
		// 1 2 3 4 5

		for (int i = 1; i <= number; i++) {
			for (int j = 1; j <= i; j++) {
				System.out.print(j + " ");
			}
			System.out.println();
		}

	}

}
```


### /08-Loops/src/com/in28minutes/loops/MyNumberRunner.java

```java
package com.in28minutes.loops;

import com.in28minutes.loops.MyNumber;

public class MyNumberRunner {

	public static void main(String[] args) {
		MyNumber number = new MyNumber(5);
		
		boolean isPrime = number.isPrime();
		System.out.println("isPrime " + isPrime);
		
		int sum = number.sumUptoN();
		System.out.println("sumUptoN " + sum);
		
		int sumOfDivisors = number.sumOfDivisors();
		System.out.println("sumOfDivisors " + sumOfDivisors);
		
		number.printNumberTriangle();
	}

}
```


### /08-Loops/src/com/in28minutes/loops/WhileNumberPlayer.java

```java
package com.in28minutes.loops;

public class WhileNumberPlayer {

	private int limit;

	public WhileNumberPlayer(int limit) {
		this.limit = limit;
	}

	// For limit = 30, output would be 1 4 9 16 25
	public void printSquaresUptoLimit() {
		int i = 1;
		while (i * i < limit) {
			System.out.print(i * i + " ");
			i++;
		}
		System.out.println();
	}

	// For limit = 27, output would be 1 8 27
	public void printCubesUptoLimit() {
		int i = 1;
		while (i * i * i <= limit) {
			System.out.print(i * i * i + " ");
			i++;
		}
		System.out.println();
	}

}
```


### /08-Loops/src/com/in28minutes/loops/WhileNumberPlayerRunner.java

```java
package com.in28minutes.loops;

public class WhileNumberPlayerRunner {
	public static void main(String[] args) {
		WhileNumberPlayer player = new WhileNumberPlayer(27);
		player.printSquaresUptoLimit();
		player.printCubesUptoLimit();
	}
}
```


# 09-ReferenceTypes

## Steps
- Step 00 - Java Reference Types - Section Introduction
- Step 01 - Reference Types - How are they stored in Memory?
- Step 02 - Java Reference Types - Puzzles
- Step 03 - String class - Introduction and Exercise - Print each word and char on a new line
- Step 04 - String class - Exercise Solution and Some More Important Methods
- Step 05 - Understanding String is Immutable and String Concat, Upper Case, Lower Case, Trim methods
- Step 06 - String Concatenation and Join, Replace Methods
- Step 07 - Java String Alternatives - StringBuffer and StringBuilder
- Step 08 - Java Wrapper Classes - An Introduction - Why and What?
- Step 09 - Java Wrapper Classes - Creation - Constructor and valueOf 
- Step 10 - Java Wrapper Classes - Auto Boxing and a Few Wrapper Constants - SIZE, BYTES, MAX_VALUE and MIN_VALUE
- Step 11 - Java Dates - Introduction to LocalDate, LocalTime and LocalDateTime
- Step 12 - Java Dates - Exploring LocalDate - Creation and Methods to play with Date
- Step 13 - Java Dates - Exploring LocalDate - Comparing Dates and Creating Specific Dates
- Step 14 - Java Reference Types - Conclusion

## Exercises

#### String
- Take a piece of Text into a String. 
   - Print each character in the text on a seperate line
   - Print each word in the text on a seperate line


## Code Examples

### /09-ReferenceTypes/commands.txt

```java
class Planet {
}
Planet jupiter = new Planet();
int i = 5;
class Animal {
    int id;
    Animal(int id) {
       this.id = id;
    }
}
Animal nothing;
nothing = cat
nothing.id = 10
cat.id
nothing = dog
nothing.id
int j = i;
j = 6
i
i == j
j = 5
i == j
Animal dog = new Animal(12);
Animal cat = new Animal(10);
Animal ref = cat;
Animal dog2 = new Animal(12);
cat == dog
cat == ref
dog == dog2
1
2
12.34
"Test".length()
BigDecimal bd = new BigDecimal("1.0");
str.charAt(0)
str.charAt(2)
str.charAt(3)
String biggerString = "This is a lot of text";
str.substring(5)
biggerString.substring(5)
biggerString.substring(5,13)
str.charAt(13)
biggerString.charAt(13)
biggerString.charAt(456)
someString.length()
someString.charAt(5)
for(int i= 0; i<someString.length(); i++) {
    System.out.println(someString.charAt(i));
}
someString.indexOf("lot")
someString.charAt(10)
someString.charAt('i')
someString.indexOf('i')
someString.lastIndexOf('i')
someString.contains("text")
String someString = "This is a lot of text again";
someString.startsWith("This")
someString.startsWith("jfsdklfj")
someString.endsWith("jfsdklfj")
someString.endsWith("in")
someString.endsWith("ain")
someString.endsWith("again")
someString.endsWith("againfsda")
someString.isEmpty()
"fjsadlkfj".isEmpty()
"".isEmpty()
"true".equals("true")
"value".equals("value")
str.equals("value")
str.equals("VAlue")
str.equalsIgnoreCase("VAlue")
str.concat("is awesome");
str
String anotherString = str.concat(" is awesome");
str
anotherString
String string2 = anotherString.concat(".");
str
anotherString
string2
str.toUpperCase()
str.toLowerCase()
str2.trim()
String str2 = "  in28Minutes is awesome.   ";
str2.trim()
1 + 2
"1" + "2"
"1" + 2
"1" + 23
1 + 23
1 + 2 + "3"
"1" + 2 + 3
System.out.println("Value is " + 20)
System.out.println("Value is " + 20 + 20)
System.out.println("Value is " + (20 + 20))
String.join(",", "2", "3", "4")
String.join(",", "A", "B","C")
String.join(",", "A")
String.join(",", "A", "B")
"abcd".replace('a', 'z');
"abcd".replace("ab", "xyz");
String str = "jdsfja ";
"123" + "123" + "1234" + "123456"
sb.append(" 123")
sb
sb
sb.setCharAt(1,'e')
sb
StringBuilder sb = new StringBuilder("test");
Integer integer1 = new Integer("5234");
Integer integer2 = new Integer("5234");
Integer i1 = new Integer(5);
Integer i2 = new Integer(5);
Integer i3 = Integer.valueOf(5);
Integer i4 = Integer.valueOf(5);
i1 == i2
i3 == i4
Integer integer = Integer.valueOf("4567");
int i = integer.intValue();
Float f = Float.valueOf("12.45");
f.floatValue()
f.intValue()
Integer eight = Integer.valueOf(8);
Integer.toBinaryString(eight);
Integer.toHexString(eight);
Integer eightyEight = Integer.valueOf(88);
Integer.toHexString(eightyEight);
seven++
seven
seven == sevenAgain
Integer seven = 7;
Integer sevenAgain = 7;
seven == sevenAgain
Integer.MAX_VALUE
Integer.MIN_VALUE
Integer.SIZE
Integer.BYTES
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.*;
today.getYear()
today.getDayOfWeek()
today.getDayOfMonth()
today.getDayOfYear()
today.getMonth()
today.getMonthValue()
today.isLeapYear()
today.lengthOfYear()
today.lengthOfMonth()
today.plusDays(100)
today.plusMonths(100)
today.plusYears(100)
today.minusYears(100)
LocalDate hundredYearsBefore = today.minusYears(100);
today
LocalDateTime now = LocalDateTime.now();
LocalDate today = LocalDate.now();
LocalDate yesterady = LocalDate.of(2018, 01, 31);
LocalDate yesterday = LocalDate.of(2018, 01, 31);
today
yesterday
today.withYear(2016)
today.withDayOfMonth(20)
today.withMonth(3)
today.withDayOfYear(120)
today.isBefore(yesterday)
today.isAfter(yesterday)
```


# 10-ArraysAndArrayList

## Steps
- Step 00 - Introduction to Array and ArrayList - Section Introduction with a Challenge
- Step 01 - Understanding the need and Basics about an Array
- Step 02 - Java Arrays - Creating and Accessing Values - Introduction
- Step 03 - Java Arrays - Puzzles - Arrays of Objects, Primitive Data Types, toString and Exceptions
- Step 04 - Java Arrays - Compare, Sort and Fill
- Step 05 - Java Arrays - Exercise - Create Student Class - Part 1 - Total and Average Marks
- Step 06 - Java Arrays - Exercise - Create Student Class - Part 2 - Maximum and Minimum Mark
- Step 07 - Introduction to Variable Arguments - Need
- Step 08 - Introduction to Variable Arguments - Basics
- Step 09 - Introduction to Variable Arguments - Enhancing Student Class
- Step 10 - Java Arrays - Using Person Objects and String Elements with Exercises
- Step 11 - Java String Arrays - Exercise Solutions - Print Day of Week with Most number of letters and more
- Step 12 - Adding and Removing Marks - Problem with Arrays
- Step 13 - First Look at ArrayList - An Introduction
- Step 14 - First Look at ArrayList - Refactoring Student Class to use ArrayList
- Step 15 - First Look at ArrayList - Enhancing Student Class with Add and Remove Marks
- Step 16 - Introduction to Array and ArrayList - Conclusion

## Exercises

#### Student Class

```java
Student student = new Student (name, list of marks);
int number = student.getNumberOfMarks();
int sum = student.getTotalSumOfMarks();
int maximumMark = student.getMaximumMark();
int minimumMark = student.getMinimumMark();
BigDecimal average = student.getAverageMarks();
student.addNewMark(35);
student.removeMarkAtIndex(5);
```

#### String Arrays
- Create a string array with days of the week
   - "Sunday", "Monday", "Tuesday", "Wednesday"
   - "Thursday", "Friday", "Saturday"
- Find the day with most number of letters in it 
   - Longest String
- Print days of the week backwards


## Code Examples

### /10-ArraysAndArrayList/src/com/in28minutes/arrays/StringRunner.java

```java
package com.in28minutes.arrays;

public class StringRunner {

	public static void main(String[] args) {

		String[] daysOfWeek = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };

		String dayWithMostCharacters = "";

		for (String day : daysOfWeek) {
			if (day.length() > dayWithMostCharacters.length()) {
				dayWithMostCharacters = day;
			}
		}

		System.out.println("Day with Most number of characters " + dayWithMostCharacters);

		for (int i = daysOfWeek.length - 1; i >= 0; i--) {
			System.out.println(daysOfWeek[i]);
		}

	}

}
```


### /10-ArraysAndArrayList/src/com/in28minutes/arrays/Student.java

```java
package com.in28minutes.arrays;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.ArrayList;
import java.util.Collections;

public class Student {

	private String name;
	private ArrayList<Integer> marks = new ArrayList<Integer>();

	public Student(String name, int... marks) {
		this.name = name;

		for (int mark : marks) {
			this.marks.add(mark);
		}
	}

	public int getNumberOfMarks() {
		return marks.size();
	}

	public int getTotalSumOfMarks() {
		int sum = 0;
		for (int mark : marks) {
			sum += mark;
		}
		return sum;
	}

	public int getMaximumMark() {
		return Collections.max(marks);
	}

	public int getMinimumMark() {
		return Collections.min(marks);
	}

	public BigDecimal getAverageMarks() {
		int sum = getTotalSumOfMarks();
		int number = getNumberOfMarks();

		return new BigDecimal(sum).divide(new BigDecimal(number), 3, RoundingMode.UP);
	}

	public String toString() {
		return name + marks;
	}

	public void addNewMark(int mark) {
		marks.add(mark);
	}

	public void removeMarkAtIndex(int index) {
		marks.remove(index);
		
	}
}
```


### /10-ArraysAndArrayList/src/com/in28minutes/arrays/StudentRunner.java

```java
package com.in28minutes.arrays;

import java.math.BigDecimal;

public class StudentRunner {

	public static void main(String[] args) {
				
		Student student = new Student("Ranga", 97, 98, 100);
				
		int number = student.getNumberOfMarks();
		System.out.println("number of marks : " + number);
		
		int sum = student.getTotalSumOfMarks();
		System.out.println("sum of marks : " + sum);
		
		int maximumMark = student.getMaximumMark();
		System.out.println("maximum of marks : " + maximumMark);
		
		int minimumMark = student.getMinimumMark();
		System.out.println("minimum of marks : " + minimumMark);
		
		BigDecimal average = student.getAverageMarks();
		System.out.println("average : " + average);
		
		System.out.println(student);
		
		student.addNewMark(35);
		
		System.out.println(student);

		student.removeMarkAtIndex(1);
		
		System.out.println(student);
		
	}

}
```


# 11-ObjectOrientedProgrammingAgain

## Steps

- Step 00 - Object Oriented Programming - Level 2 - Section Introduction
- Step 01 - Basics of Designing a Class - Class, Object, State and Behavior
- Step 02 - OOPS Example - Fan Class - Deciding State and Constructors
- Step 03 - OOPS Example - Fan Class - Deciding Behavior with Methods
- Step 04 - OOPS Exercise - Rectangle Class
- Step 05 - Understanding Object Composition with Customer Address Example
- Step 06 - Understanding Object Composition - An Exercise - Books and Reviews
- Step 07 - Understanding Inheritance - Why do we need it?
- Step 08 - Object is at top of Inheritance Hierarchy
- Step 09 - Inheritance and Overriding - with toString() method
- Step 10 - Java Inheritance - Exercise - Student and Employee Classes
- Step 11 - Java Inheritance - Default Constructors and super() method call
- Step 12 - Java Inheritance - Puzzles - Multiple Inheritance, Reference Variables and instanceof

- Step 13 - Java Abstract Class - Introductio
- Step 14 - Java Abstract Class - First Example - Creating Recipes with Template Method
- Step 15 - Java Abstract Class - Puzzles
- Step 16 - Java Interface - Example 1 - Gaming Console - How to think about Intefaces? 
- Step 17 - Java Interface - Example 2 - Complex Algorithm - API defined by external team
- Step 18 - Java Interface - Puzzles - Unimplemented methods, Abstract Classes, Variables, Default Methods and more
- Step 19 - Java Interface vs Abstract Class - A Comparison
- Step 20 - Java Interface Flyable and Abstract Class Animal - An Exercise
- Step 21 - Polymorphism - An introduction

## Exercises

#### Creating a simple class
- public class Rectangle
  - length, width;
  - What constructors?
  - What Operations?

#### Object Composition - Book and Reviews

Object Composition
- Book - id, name, author
  - Reviews - id, description, rating

```java 
 Book book = 
    new Book(123, "Object Oriented Programming with Java", 
          "Ranga");
 book.addReview(
    new Review(10, "Great Book", 5));
 book.addReview(
    new Review(101, "Awesome", 5);

 System.out.println(book);
 ```

#### Inheritance

Setup an Inheritance Hierarchy and implement toString in Employee class
- Person
   - name,phone,email;
- Student 
  - college, class
- Employee 
  - title, employer, employeeGrade, salary
  - toString (print all values including those of Person)

#### Interface and Abstract Class

interface Flyable 
- void fly();
- Bird "with wings"
- Aeroplane "with fuel"
- Flyable flyingObjects = {new Bird(), new Aeroplane()};
- Loop and invoke fly method

abstract class Animal
- void bark()
- Dog "Bow Bow"
- Cat "Meow Meow"
- Animal[] animals = {new Cat(), new Dog()};
- Loop and invoke bark method

## Code Examples

### /commands.txt

```java
class Pet extends Animal {
     public void groom() {
        System.out.println("Groom");
     }
}
dog.toString()
dog.groom()
Pet pet = new Dog();
pet.groom()
pet instanceof Pet
pet instanceof Dog
pet instanceof Animal
pet instanceof Object
animal instanceof Pet
animal instanceof Dog
animal instanceof Object
class Animal {
   public void bark() {
       System.out.println("TEst");
   }
}
animal.bark()
abstract class AbstractAnimal {
    abstract public void bark();
}
class Dog extends AbstractAnimal {
    public void bark() {
       System.out.println("Bow Bow");
    }
}
Dog dog = new Dog();
dog.bark()
abstract class AbstractTest {
}
abstract class Algorithm1 extends AbstractAlgorithm {
}
abstract class AbstractAlgorithm {
     private int stepCount;
     public int getStepCount() {
          return stepCount();
     }
}
class Implementation implements Interface2 {
   public void method2() { }
   public void method1() { }
}
abstract class ImplementationAbstract implements Interface2 {
   public void method1() { }
}
interface Interface3 {
  int test = 5;
}
interface Interface4 {
    default void print() {
       System.out.println("default");
    }
}
class Test implements Interface4 {
}
test.print()
class Test1 implements Interface4 {
   public void print() {
      System.out.println("override");
   }
}
Test1 test = new Test1();
test.print()
interface Interface1 {
 void method1();
}
interface Interface2 {
 void method2();
}
```


### /src/com/in28minutes/oops/level2/AbstractRecipe.java

```java
package com.in28minutes.oops.level2;

public abstract class AbstractRecipe {
	
	public void execute() {
		getReady();
		doTheDish();
		cleanup();
	}
	
	abstract void getReady();
	abstract void doTheDish();
	abstract void cleanup();
}
```


### /src/com/in28minutes/oops/level2/Address.java

```java
package com.in28minutes.oops.level2;

public class Address {
	private String line1;
	private String city;
	private String zip;
	
	//creation
	public Address(String line1, String city, String zip) {
		super();
		this.line1 = line1;
		this.city = city;
		this.zip = zip;
	}
	
	public String toString() {
		return line1 + " " + city + " " + zip;
				 
	}
	
}
```


### /src/com/in28minutes/oops/level2/Book.java

```java
package com.in28minutes.oops.level2;

import java.util.ArrayList;

public class Book {

	private int id;
	private String name;
	private String author;
	private ArrayList<Review> reviews = new ArrayList<>();

	public Book(int id, String name, String author) {
		this.id = id;
		this.name = name;
		this.author = author;
	}

	public void addReview(Review review) {
		this.reviews.add(review);
	}
	
	public String toString() {
		return String.format("id =%d name = %s author = %s Reviews = [%s]",
				id, name, author, reviews);
	}

}
```


### /src/com/in28minutes/oops/level2/BookRunner.java

```java
package com.in28minutes.oops.level2;

public class BookRunner {

	public static void main(String[] args) {
		Book book = new Book(123, "Object Oriented Programming with Java",
				"Ranga");
		book.addReview(new Review(10, "Great Book", 5));
		book.addReview(new Review(101, "Awesome", 5));

		System.out.println(book);

	}

}
```


### /src/com/in28minutes/oops/level2/Customer.java

```java
package com.in28minutes.oops.level2;

public class Customer {

	//state
	private String name;
	private Address homeAddress;
	private Address workAddress;
	
	//creating
	public Customer(String name, Address homeAddress) {
		this.name = name;
		this.homeAddress = homeAddress;
	}

	//operations
	public Address getHomeAddress() {
		return homeAddress;
	}

	public void setHomeAddress(Address homeAddress) {
		this.homeAddress = homeAddress;
	}

	public Address getWorkAddress() {
		return workAddress;
	}

	public void setWorkAddress(Address workAddress) {
		this.workAddress = workAddress;
	}
		
	public String toString() {
		return String.format("name - [%s] home address - [%s] work address - [%s])"
				, name, homeAddress, workAddress);
	}
	
}
```


### /src/com/in28minutes/oops/level2/CustomerRunner.java

```java
package com.in28minutes.oops.level2;

public class CustomerRunner {

	public static void main(String[] args) {
		Address homeAddress = new Address("line 1", "Hyderabad", "500035");
		Customer customer = new Customer("Ranga", homeAddress);
		System.out.println(customer);
		
		Address workAddress = new Address("line 1 for work", "Hyderabad", "500078");
		customer.setWorkAddress(workAddress);
		
		System.out.println(customer);
	}	
}
```


### /src/com/in28minutes/oops/level2/Fan.java

```java
package com.in28minutes.oops.level2;

public class Fan {
	
	//state
	private String make;
	private double radius;
	private String color;

	private boolean isOn;
	private byte speed; //0 to 5
	
	//creation
	public Fan(String make, double radius, String color) {
		this.make = make;
		this.radius = radius;
		this.color = color;
	}
	
	public void switchOn() {
		this.isOn = true;
		setSpeed((byte)5);
	}

	public void switchOff() {
		this.isOn = false;
		setSpeed((byte)0);
	}

	public void setSpeed(byte speed) {
		this.speed = speed;
	}
	
	//print the state
	public String toString() {
		return String.format("make - %s, radius - %f , color - %s , isOn - %b , speed - %d", 
				make, radius, color, isOn, speed);
	}
	
}
```


### /src/com/in28minutes/oops/level2/FanRunner.java

```java
package com.in28minutes.oops.level2;

public class FanRunner {
	public static void main(String[] args) {
		Fan fan = new Fan("Manufacturer 1", 0.34567, "GREEN");
		fan.switchOn();
		System.out.println(fan);
		fan.setSpeed((byte)3);
		System.out.println(fan);
		fan.switchOff();
		System.out.println(fan);
	}
}
```


### /src/com/in28minutes/oops/level2/inheritance/AnimalRunner.java

```java
package com.in28minutes.oops.level2.inheritance;

abstract class Animal {
	abstract void bark();
}

class Dog extends Animal {
	public void bark() {
		System.out.println("Bow Bow");
	}
}

class Cat extends Animal {
	public void bark() {
		System.out.println("Meow Meow");
	}
}

public class AnimalRunner {
	public static void main(String[] args) {
		Animal[] animals = {new Cat(), new Dog()};
		for(Animal animal:animals) {
			animal.bark();
		}

	}

}
```


### /src/com/in28minutes/oops/level2/inheritance/Employee.java

```java
package com.in28minutes.oops.level2.inheritance;

import java.math.BigDecimal;

public class Employee extends Person {
	private String title;
	private String employerName;
	private char employeeGrade;
	private BigDecimal salary;
	
	public Employee(String name, String title) {
		super(name);
		this.title = title;
		System.out.println("Employee Constructor");
	}

	public String getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public String getEmployerName() {
		return employerName;
	}

	public void setEmployerName(String employerName) {
		this.employerName = employerName;
	}

	public char getEmployeeGrade() {
		return employeeGrade;
	}

	public void setEmployeeGrade(char employeeGrade) {
		this.employeeGrade = employeeGrade;
	}

	public BigDecimal getSalary() {
		return salary;
	}

	public void setSalary(BigDecimal salary) {
		this.salary = salary;
	}

	public String toString() {
        return super.toString() + "#" + title + "#" + employerName + "#" + employeeGrade;
    }

}
```


### /src/com/in28minutes/oops/level2/inheritance/Person.java

```java
package com.in28minutes.oops.level2.inheritance;

public class Person extends Object{
	private String name;
	private String email;
	private String phoneNumber;
		
	public Person(String name) {
		System.out.println("Person Constructor");
		this.name = name;
	}
	
	public String getName() {
		return name;
	}

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public String getPhoneNumber() {
		return phoneNumber;
	}

	public void setPhoneNumber(String phoneNumber) {
		this.phoneNumber = phoneNumber;
	}
	
	public String toString() {
        return name + "#" + email + "#" + phoneNumber;
    }
}
```


### /src/com/in28minutes/oops/level2/inheritance/Student.java

```java
package com.in28minutes.oops.level2.inheritance;

public class Student extends Person {
	private String collegeName;
	private int year;

	public Student(String name, String collegeName) {
		super(name);
		this.collegeName = collegeName;
	}
	
	public String getCollegeName() {
		return collegeName;
	}

	public void setCollegeName(String collegeName) {
		this.collegeName = collegeName;
	}

	public int getYear() {
		return year;
	}

	public void setYear(int year) {
		this.year = year;
	}

}
```


### /src/com/in28minutes/oops/level2/inheritance/StudentRunner.java

```java
package com.in28minutes.oops.level2.inheritance;

public class StudentRunner {

	public static void main(String[] args) {
		
		//Student student = new Student();
		//student.setName("Ranga");
		//student.setEmail("in28minutes@gmail.com");
		
		/*
		Person person = new Person();
		person.setName("Ranga");
		person.setEmail("ranga@in28minutes.com");
		person.setPhoneNumber("123-456-7890");
		String value = person.toString();
		System.out.println(value);
		System.out.println(person);
		*/
		
		Employee employee = new Employee("Ranga", "Programmer Analyst");
		//employee.setName("Ranga");
		employee.setEmail("ranga@in28minutes.com");
		employee.setPhoneNumber("123-456-7890");
		employee.setEmployeeGrade('A');
		employee.setTitle("Programmer Analyst");
		
		System.out.print(employee);
		
	}
}
```


### /src/com/in28minutes/oops/level2/inheritance/StudentWithoutInheritance.java

```java
package com.in28minutes.oops.level2.inheritance;

public class StudentWithoutInheritance {
	private String name;
	private String email;
	private String phoneNumber;
	
	private String college;
	private int year;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public String getPhoneNumber() {
		return phoneNumber;
	}

	public void setPhoneNumber(String phoneNumber) {
		this.phoneNumber = phoneNumber;
	}

	public String getCollege() {
		return college;
	}

	public void setCollege(String college) {
		this.college = college;
	}

	public int getYear() {
		return year;
	}

	public void setYear(int year) {
		this.year = year;
	}

	
	
}
```


### /src/com/in28minutes/oops/level2/interfaces/ChessGame.java

```java
package com.in28minutes.oops.level2.interfaces;

public class ChessGame implements GamingConsole{

	@Override
	public void up() {
		System.out.println("Move piece up");
	}

	@Override
	public void down() {
		System.out.println("Move piece down");
	}

	@Override
	public void left() {
		System.out.println("Move piece left");
	}

	@Override
	public void right() {
		System.out.println("Move piece right");
	}
	
}
```


### /src/com/in28minutes/oops/level2/interfaces/ComplexAlgorithm.java

```java
package com.in28minutes.oops.level2.interfaces;

public interface ComplexAlgorithm {
	int complexAlgorithm(int number1, int number2);
}
```


### /src/com/in28minutes/oops/level2/interfaces/DummyAlgorithm.java

```java
package com.in28minutes.oops.level2.interfaces;

public class DummyAlgorithm implements ComplexAlgorithm{

	@Override
	public int complexAlgorithm(int number1, int number2) {
		return number1 + number2;
	}

}
```


### /src/com/in28minutes/oops/level2/interfaces/FlyableRunner.java

```java
package com.in28minutes.oops.level2.interfaces;

interface Flyable{
	void fly();
}

class Bird implements Flyable{

	@Override
	public void fly() {
		System.out.println("with wings");
	}
	
}

class Aeroplane implements Flyable{

	@Override
	public void fly() {
		System.out.println("with fuel");
	}
	
}

public class FlyableRunner {

	public static void main(String[] args) {
		Flyable[] flyingObjects = { new Bird(), new Aeroplane()};
		for(Flyable object : flyingObjects) {
			object.fly();
		}
	}

}
```


### /src/com/in28minutes/oops/level2/interfaces/GameRunner.java

```java
package com.in28minutes.oops.level2.interfaces;

public class GameRunner {

	public static void main(String[] args) {
		GamingConsole[] games = {new MarioGame(), new ChessGame()};
		
		for(GamingConsole game:games) {
			game.up();
			game.down();
			game.left();
			game.right();
		}

	}

}
```


### /src/com/in28minutes/oops/level2/interfaces/GamingConsole.java

```java
package com.in28minutes.oops.level2.interfaces;

public interface GamingConsole {
	public void up();
	public void down();
	public void left();
	public void right();
}
```


### /src/com/in28minutes/oops/level2/interfaces/MarioGame.java

```java
package com.in28minutes.oops.level2.interfaces;

public class MarioGame implements GamingConsole{

	@Override
	public void up() {
		System.out.println("Jump");
	}

	@Override
	public void down() {
		System.out.println("Goes into a hole");
	}

	@Override
	public void left() {
	}

	@Override
	public void right() {
		System.out.println("Go Forward");
	}
	
}
```


### /src/com/in28minutes/oops/level2/interfaces/Project.java

```java
package com.in28minutes.oops.level2.interfaces;

public class Project {

	interface Test {
		void nothing();

		default void nothing1() {

		}

	}

	class Class1 implements Test {

		@Override
		public void nothing() {
			// TODO Auto-generated method stub

		}

	}

	class Class2 implements Test {

		@Override
		public void nothing() {
			// TODO Auto-generated method stub

		}

	}

	public static void main(String[] args) {
		ComplexAlgorithm algorithm = new RealAlgorithm();
		System.out.println(algorithm.complexAlgorithm(10, 20));
	}

}
```


### /src/com/in28minutes/oops/level2/interfaces/RealAlgorithm.java

```java
package com.in28minutes.oops.level2.interfaces;

public class RealAlgorithm implements ComplexAlgorithm{

	@Override
	public int complexAlgorithm(int number1, int number2) {
		return number1 * number2;
	}

}
```


### /src/com/in28minutes/oops/level2/Recipe1.java

```java
package com.in28minutes.oops.level2;

public class Recipe1 extends AbstractRecipe{

	@Override
	void getReady() {
		System.out.println("Get the raw materials");
		System.out.println("Get the utensils");
	}

	@Override
	void doTheDish() {
		System.out.println("do the dish");
	}

	@Override
	void cleanup() {
		System.out.println("Cleanup the utensils");		
	}

}
```


### /src/com/in28minutes/oops/level2/RecipeRunner.java

```java
package com.in28minutes.oops.level2;

public class RecipeRunner {

	public static void main(String[] args) {
		Recipe1 recipe = new Recipe1();
		recipe.execute();

		RecipeWithMicrowave recipeWithMicrowave = new RecipeWithMicrowave();
		recipeWithMicrowave.execute();

	}

}
```


### /src/com/in28minutes/oops/level2/RecipeWithMicrowave.java

```java
package com.in28minutes.oops.level2;

public class RecipeWithMicrowave extends AbstractRecipe{

	@Override
	void getReady() {
		System.out.println("Get the raw materials");
		System.out.println("Switch on the microwave");
	}

	@Override
	void doTheDish() {
		System.out.println("get stuff ready");
		System.out.println("Put it in the microwave");
	}

	@Override
	void cleanup() {
		System.out.println("Cleanup the utensils");
		System.out.println("Switch off the microwave");
	}

}
```


### /src/com/in28minutes/oops/level2/Rectangle.java

```java
package com.in28minutes.oops.level2;

public class Rectangle {

	//state
	private int length;
	private int width;
	
	//creation
	public Rectangle(int length, int width) {
		this.length = length;
		this.width = width;
	}


	//operations
	public int getLength() {
		return length;
	}

	public void setLength(int length) {
		this.length = length;
	}

	public int getWidth() {
		return width;
	}

	public void setWidth(int width) {
		this.width = width;
	}
		
	public int area() {
		return length * width;
	}
	
	public int perimeter() {
		return 2 * (length + width);
	}
	
	public String toString() {
		return String.format("length - %d width - %d area - %d perimeter - %d", 
				length, width, area(), perimeter());
	}
}
```


### /src/com/in28minutes/oops/level2/RectangleRunner.java

```java
package com.in28minutes.oops.level2;

public class RectangleRunner {

	public static void main(String[] args) {
		Rectangle rectangle = new Rectangle(12, 23);
		System.out.println(rectangle);
		rectangle.setWidth(25);
		System.out.println(rectangle);
	}

}
```


### /src/com/in28minutes/oops/level2/Review.java

```java
package com.in28minutes.oops.level2;

public class Review {

	private int id;
	private String description;
	private int rating;

	public Review(int id, String description, int rating) {
		this.id = id;
		this.description = description;
		this.rating = rating;
	}
	
	public String toString() {
		return id + " " + description + " " + rating;
	}

}
```


# 12-Collections

## Steps
- Step 01 - Java Collections - Section Overview with Need For Collections
- Step 02 - List Interface - Introduction - Position is King
- Step 03 - List Inteface - Immutability and Introduction of Implementations - ArrayList, LinkedList and Vector
- Step 04 - List Inteface Implementations - ArrayList vs LinkedList
- Step 05 - List Inteface Implementations - ArrayList vs Vector
- Step 06 - List Inteface - Methods to add, remove and change elements and lists 
- Step 07 - List and ArrayList - Iterating around elements
- Step 08 - List and ArrayList - Choosing iteration approach for printing and deleting elements
- Step 09 - List and ArrayList - Puzzles - Type Safety and Removing Integers
- Step 10 - List and ArrayList - Sorting - Introduction to Collections sort static method
- Step 11 - List and ArrayList - Sorting - Implementing Comparable Inteface in Student Class
- Step 12 - List and ArrayList - Sorting - Providing Flexibility by implementing Comparator interface
- Step 13 - List and ArrayList - A Summary
- Step 14 - Set Interface - Introduction - No Duplication 
- Step 15 - Understanding Data Structures - Array, LinkedList and Hashing
- Step 16 - Understanding Data Structures - Tree - Sorted Order
- Step 17 - Set Interface - Hands on - HashSet, LinkedHashSet and TreeSet
- Step 18 - Set Interface - Exercise - Find Unique Characters in a List
- Step 19 - TreeSet - Methods from NavigableSet - floor,lower,upper, subSet, head and tailSet
- Step 20 - Queue Interface - Process Elements in Order
- Step 21 - Introduction to PriorityQueue - Basic Methods and Customized Priority
- Step 22 - Map Interface - An Introduction - Key and Value
- Step 23 - Map Interface - Implementations - HashMap, HashTable, LinkedHashMap and TreeMap
- Step 24 - Map Interface - Basic Operations
- Step 25 - Map Interface - Comparison - HashMap vs LinkedHashMap vs TreeMap
- Step 26 - Map Interface - Exercise - Count occurances of characters and words in a piece of text
- Step 27 - TreeMap - Methods from NavigableMap - floorKey, higherKey, firstEntry, subMap and more
- Step 28 - Java Collections - Conclusion with Three Tips

## Exercises

#### Set Interface
- Find unique characters in a list of characters
   - In Insertion Order
   - In Sort Order

#### Map Interface
- Find number of occurances of each character and word in a piece of text.  

## Code Examples

### /12-Collections/commands.txt

```java
words.size()
words.isEmpty()
words.get(0)
words.contains("Dog");
words.contains("Cat");
words.indexOf("Cat")
words
words.indexOf("Dog")
words.add("Dog")
List<String> wordsLinkedList = new LinkedList<String>(words);
List<String> wordsVector = new Vector<String>(words);
wordsArrayList.add("Dog")
wordsArrayList
wordsArrayList.add("Elephant")
wordsArrayList.add(2, "Ball")
wordsArrayList
wordsArrayList.add("Ball")
wordsArrayList
List<String> newList = List.of("Yak","Zebra");
wordsArrayList.addAll(newList)
wordsArrayList
wordsArrayList.set(6, "Fish")
wordsArrayList
wordsArrayList.remove(2)
wordsArrayList
wordsArrayList.remove("Dog")
wordsArrayList
wordsArrayList.remove("Dog")
for(int i=0; i < words.size(); i++) {
     System.out.println(words.get(i));
}
for(String word:words) {
     System.out.println(word);
}
Iterator wordsIterator = words.iterator();
while(wordsIterator.hasNext()) {
      System.out.println(wordsIterator.next());
}
List<String> wordsArrayList = new ArrayList<String>(words);
for(String word:words) {
   if(word.endsWith("at")) {
        words.remove(word);
   }
}
for(String word:wordsArrayList) {
   if(word.endsWith("at")) {
        wordsArrayList.remove(word);
   }
}
wordsArrayList
for(String word:words) {
   if(word.endsWith("at"))
      System.out.println(word);
}
for(String word:wordsAl) {
   if(word.endsWith("at")) {
        words.remove(word);
   }
}
for(String word:wordsAl) {
   if(word.endsWith("at")) {
        wordsAl.remove(word);
   }
}
wordsAl
List<String> words = List.of("Apple", "Bat" , "Cat");
List<String> wordsAl = new ArrayList<>(words);
Iterator<String> iterator = wordsAl.iterator();
while(iterator.hasNext()) {
     if(iterator.next().endsWith("at")) {
          iterator.remove();
     }
}
wordsAl
List value = List.of("A", 'A' , 1, 1.0);
value.get(2)
value.get(2) instanceof Integer
value.get(1) instanceof Character
value.get(3) instanceof Double
numbers.indexOf(101);
numbersAl.indexOf(101)
numbersAl.remove(101);
numbersAl.remove(101)
numbersAl.remove(Integer.valueOf(101))
numbersAl
List<Integer> numbersAl = new ArrayList<>(numbers);
Collections.sort(numbersAl);
numbersAl
set.add("Apple");
Set<String> hashset = new HashSet<>(set);
hashset.add("Apple")
hashset
Set<String> set = Set.of("A", "Z","D", "C", "B");
hashSet.add("A")
hashSet.add("B")
hashSet
hashSet.add("C")
hashSet
hashSet.add("CA")
hashSet
hashSet.add("CAfsadfa")
hashSet
treeSet.add("Cat")
treeSet.add("Bat")
treeSet.add("Apple")
treeSet
hashSet.add("Cat");
hashSet.add("Bat");
hashSet.add("Apple");
hashSet
hashSet.add("Dog");
hashSet
hashSet.add("Elephant");
hashSet.add(5);
hashSet.add(4);
hashSet.add(3);
hashSet.add(2);
hashSet.add(1);
hashSet
Set<Integer> hashSet = new HashSet<>();
hashSet.add(589789);
hashSet.add(58978);
hashSet.add(5897);
hashSet.add(589);
hashSet.add(58);
hashSet.add(5);
hashSet
Set<Integer> linkedHashSet = new LinkedHashSet<>();
linkedHashSet.add(589789);
linkedHashSet.add(58978);
linkedHashSet.add(5897);
linkedHashSet.add(589);
linkedHashSet.add(58);
linkedHashSet.add(5);
linkedHashSet
Set<Integer> treeSet = new TreeSet<>();
treeSet.add(584567);
treeSet.add(58456);
treeSet.add(5845);
treeSet.add(584);
treeSet.add(58);
treeSet.add(5);
treeSet
numbers.add(765432);
numbers.add(76543);
numbers.add(7654);
numbers.add(765);
numbers.add(76);
numbers
numbers.add(765432);
numbers.add(76543);
numbers.add(7654);
numbers.add(765);
numbers.add(76);
numbers
numbers.add(765789);
numbers
numbers.add(76)
numbers
numbers.add(765432);
numbers.add(76543);
numbers.add(7654);
numbers.add(765);
numbers.add(76);
numbers
numbers.add(76)
List<Character> characters = List.of('A','Z','A', 'B', 'Z','F');
TreeSet<Integer> numbers = new TreeSet<>(Set.of(65,54,34,12,99));
numbers.floor(40)
numbers.floor(34)
numbers.lower(34)
numbers.ceiling(34)
numbers.ceiling(36)
numbers.higher(34)
numbers
numbers.subSet(20,80)
numbers.subSet(34,54)
numbers.subSet(34,65)
numbers.subSet(34,true,65,true)
numbers.subSet(34,false,65,false)
numbers.headSet(50)
numbers.tailSet(50)
Queue<String> queue = new PriorityQueue<>();
queue.poll()
queue.offer("Apple")
queue.addAll(List.of("Zebra", "Monkey", "Cat"))
queue
queue.poll()
queue
queue.poll()
queue.poll()
queue.poll()
queue.poll()
map.put("R",1);
map
map.get("Z")
map.get("A")
map.get("C")
map.size()
map.isEmpty()
map.containsKey("A")
map.containsKey("F")
map.containsValue(3)
map
map.containsValue(4)
map.keySet()
map.values()
map
hashmap.put("F",5)
hashmap
hashmap.put("Z",11)
hashmap
Map<String, Integer> map = Map.of("A",3,"Z",5,"B",10);
Map<String, Integer> linkedHashmap = new LinkedHashMap<>(map);
HashMap<String, Integer> hashmap = new HashMap<>();
hashmap.put("Z",5)
hashmap.put("A",15)
hashmap.put("F",25)
hashmap.put("L",250)
hashmap
LinkedHashMap<String, Integer> linkedHashMap = new LinkedHashMap<>();
hashmap
linkedHashMap.put("F",25)
linkedHashMap.put("A",15)
linkedHashMap.put("Z",5)
linkedHashMap.put("L",250)
linkedHashMap
treemap.put("F",25)
treemap.put("A",15)
treemap.put("Z",5)
treemap.put("L",250)
treemap
TreeMap<String, Integer> treemap = new TreeMap<>();
treemap.put("F",25)
treemap.put("Z",5)
treemap.put("L",250)
treemap.put("A",15)
treemap.put("B",25)
treemap.put("G",25)
treemap
treemap.higherKey("C")
treemap.lowerKey("C")
treemap.lowerKey("B")
treemap.floorKey("B")
treemap.higherKey("B")
treemap.higherKey("C")
treemap.ceilingKey("B")
treemap.lowerKey("B")
treemap.floorKey("B")
treemap.firstEntry()
treemap.lastEntry()
treemap
treemap.subMap("C", "Y")
treemap.subMap("B", "Z")
treemap.subMap("B",true, "Z",true)
```


### /12-Collections/src/collections/MapRunner.java

```java
package collections;

import java.util.HashMap;
import java.util.Map;


public class MapRunner {

	public static void main(String[] args) {
		String str = "This is an awesome occasion. "
				+ "This has never happened before.";
		
		Map<Character, Integer> occurances = new HashMap<>();
		
		char[] characters = str.toCharArray();
		
		for(char character:characters) {
			//Get the character
			Integer integer = occurances.get(character);
			if(integer==null) {
				occurances.put(character, 1);
			} else {
				occurances.put(character, integer + 1);
			}
		}
		
		System.out.println(occurances);
		
		Map<String, Integer> stringOccurances = new HashMap<>();
		String[] words = str.split(" ");
		
		
		for(String word:words) {
			//Get the character
			Integer integer = stringOccurances.get(word);
			if(integer==null) {
				stringOccurances.put(word, 1);
			} else {
				stringOccurances.put(word, integer + 1);
			}
		}
		
		System.out.println(stringOccurances);
		
		
	}

}
```


### /12-Collections/src/collections/QueueRunner.java

```java
package collections;

import java.util.Comparator;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Queue;

class StringLengthComparator implements Comparator<String> {
	@Override
	public int compare(String value1, String value2) {
		return Integer.compare(value2.length(),
				value1.length());
	}

}

public class QueueRunner {

	public static void main(String[] args) {
		Queue<String> queue = new PriorityQueue<>(10,
				new StringLengthComparator());
		queue.addAll(List.of("Zebra", "Monkey", "Cat", "A",
				"B", "C", "D", "E", "F", "G"));
		queue.offer("Z");
		while (queue.peek() != null)
			System.out.println(queue.poll());
	}

}
```


### /12-Collections/src/collections/SetRunner.java

```java
package collections;

import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

public class SetRunner {

	public static void main(String[] args) {
		List<Character> characters = List.of('A','Z','A', 'B', 'Z','F');
		//unique - Set
		// Tree
		// Hash
		// LinkedHash
		
		Set<Character> treeSet = new TreeSet<>(characters);
		System.out.println("treeSet "+ treeSet);

		Set<Character> linkedHashSet = new LinkedHashSet<>(characters);
		System.out.println("linkedHashSet "+ linkedHashSet);
		
		Set<Character> hashSet = new HashSet<>(characters);
		System.out.println("hashSet "+ hashSet);

		

	}

}
```


### /12-Collections/src/collections/Student.java

```java
package collections;

public class Student implements Comparable<Student>{
	private int id;
	private String name;

	public Student(int id, String name) {
		super();
		this.id = id;
		this.name = name;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String toString() {
		return id + " " + name;
	}

	@Override
	public int compareTo(Student that) {
		return Integer.compare(that.id, this.id);
	}
}
```


### /12-Collections/src/collections/StudentsCollectionRunner.java

```java
package collections;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

class AscendingStudentComparator implements Comparator<Student> {
	@Override
	public int compare(Student student1, Student student2) {
		return Integer.compare(student1.getId(), student2.getId());
	}
}

public class StudentsCollectionRunner {

	public static void main(String[] args) {
		List<Student> students = List.of(new Student(1, "Ranga"),
				new Student(100, "Adam"),
				new Student(2,"Eve"));
		
		ArrayList<Student> studentsAl = new ArrayList<>(students);
		
		System.out.println(studentsAl);
		
		Collections.sort(studentsAl);
		System.out.println("Desc " + studentsAl);
		
		//Collections.sort(studentsAl, new AscendingStudentComparator());
		
		studentsAl.sort(new AscendingStudentComparator());
		System.out.println("AscendingStudentComparator " + studentsAl);	
	}

}
```


# 13-Generics

## Steps
- Step 01 - Introduction to Generics - Why do we need Generics?
- Step 02 - Implementing Generics for the Custom List
- Step 03 - Extending Custom List with a Generic Return Method
- Step 04 - Generics Puzzles - Restrictions with extends and Generic Methods
- Step 05 - Generics and WildCards - Upper Bound and Lower Bound

## Code Examples

### /13-Generics/src/com/in28minutes/generics/GenericsRunner.java

```java
package com.in28minutes.generics;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class GenericsRunner {

	static <X> X doubleValue(X value) {
		return value;
	}

	static <X extends List> void duplicate(X list) {
		list.addAll(list);
	}

	static double sumOfNumberList(
			List<? extends Number> numbers) {
		double sum = 0.0;
		for (Number number : numbers) {
			sum += number.doubleValue();
		}
		return sum;
	}

	static void addACoupleOfValues(
			List<? super Number> numbers) {
		numbers.add(1);
		numbers.add(1.0);
		numbers.add(1.0f);
		numbers.add(1l);
	}

	public static void main(String[] args) {
		List emptyList = new ArrayList<Number>();
		addACoupleOfValues(emptyList);
		System.out.println(emptyList);

		System.out.println(
				sumOfNumberList(List.of(1, 2, 3, 4, 5)));
		System.out.println(sumOfNumberList(
				List.of(1.1, 2.1, 3.1, 4.1, 5.1)));
		System.out.println(sumOfNumberList(
				List.of(1l, 2l, 3l, 4l, 5l)));

		String value1 = doubleValue(new String());
		Integer number1 = doubleValue(Integer.valueOf(5));
		ArrayList list1 = doubleValue(new ArrayList());

		LinkedList<Integer> numbers = new LinkedList<>(
				List.of(1, 2, 3));
		duplicate(numbers);
		System.out.println(numbers);

		MyCustomList<String> list = new MyCustomList<>();
		list.addElement("Element 1");
		list.addElement("Element 2");
		String value = list.get(0);

		System.out.println(value);

		MyCustomList<Integer> list2 = new MyCustomList<>();
		list2.addElement(Integer.valueOf(5));
		list2.addElement(Integer.valueOf(7));
		Integer number = list2.get(0);
		System.out.println(number);

	}

}
```


### /13-Generics/src/com/in28minutes/generics/MyCustomList.java

```java
package com.in28minutes.generics;

import java.util.ArrayList;

public class MyCustomList<T>{
	
	ArrayList<T> list = new ArrayList<>();
	
	public void addElement(T element) {
		list.add(element);
	}
	
	public void removeElement(T element) {
		list.remove(element);
	}
	
	public String toString() {
		return list.toString();
	}

	public T get(int index) {
		return list.get(index);
	}
}
```


# 14-FunctionalProgramming

## Steps
- Step 01 - Introduction to Functional Programming - Functions are First Class Citizens
- Step 02 - Functional Programming - First Example with Function as Parameter
- Step 03 - Functional Programming - Exercise - Loop a List of Numbers
- Step 04 - Functional Programming - Filtering - Exercises to print odd and even numbers from List
- Step 05 - Functional Programming - Collect - Sum of Numbers in a List
- Step 06 - Functional Programming vs Structural Programming - A Quick Comparison
- Step 07 - Functional Programming Terminology - Lambda Expression, Stream and Operations on a Stream
- Step 08 - Stream Intermediate Operations - Sort, Distinct, Filter and Map
- Step 09 - Stream Intermediate Operations - Exercises - Squares of First 10, Map String List to LowerCase and Length of String
- Step 10 - Stream Terminal Operations - 1 - max operation with Comparator 
- Step 11 - Stream Terminal Operations - 2 - min, collect to List, 
- Step 12 - Optional class in Java - An Introduction
- Step 13 - Behind the Screens with Functional Interfaces - Implement Predicate Interface
- Step 14 - Behind the Screens with Functional Interfaces - Implement Consumer Interface
- Step 15 - Behind the Screens with Functional Interfaces - Implement Function Inteface for Mapping
- Step 16 - Simplify Functional Programming code with Method References - static and instance methods
- Step 17 - Functions are First Class Citizens
- Step 18 - Introduction to Functional Programming - Conclusion

## Exercises
- Create a list of numbers
   - Print each element using forEach
   - Filter Odd and Even numbers
- Print squares of first 10 Numbers using ```IntStream.range(1,11)```
- ```List.of("Apple","Ant","Bat").stream()``` 
   - Map each to lowercase and print
   - Print length (no of characters) of each word using map

## Code Examples

### /14-FunctionalProgramming/commands.txt

```java
List<Integer> list = List.of(1,4,7,9);
list.stream().forEach(
      element -> System.out.println(element)
)
list.stream().filter(
               element -> element%2 == 1)
list.stream().filter(
               element -> element%2 == 1).
             forEach(
               element -> System.out.println(element))
list.stream().filter(element -> element%2==1).forEach(element->System.out.println(element))
list.stream().filter(element -> element%2==0).forEach(element->System.out.println(element))
numbers.stream().sorted().forEach(e->System.out.println(e));
List<Integer> numbers = List.of(3,5,3,213,45,5,7);
numbers.stream().distinct().forEach(e->System.out.println(e));
numbers.stream().distinct().sorted().forEach(e->System.out.println(e));
numbers.stream().distinct().map(e -> e * e).forEach(e->System.out.println(e));
IntStream.range(1,10).forEach(p->System.out.println(p))
IntStream.range(1,11).forEach(p->System.out.println(p))
IntStream.range(1,11).map(e -> e * e).forEach(p->System.out.println(p))
List.of("Apple", "Ant", "Bat").stream().map(s->s.toLowerCase()).forEach(p -> System.out.println(p))
List.of("Apple", "Ant", "Bat").stream().map(s->s.length()).forEach(p -> System.out.println(p))
IntStream.range(1,11).reduce( 0 , (n1,n2) -> n1+n2)
List.of(23,12,34,53).stream().max((n1,n2) -> Integer.compare(n1,n2))
$24.isPresent()
List.of(23,12,34,53).stream().max((n1,n2) -> Integer.compare(n1,n2)).get()
List.of(23,12,34,53).stream().max((n1,n2) -> Integer.compare(n1,n2)).get()
List.of(23,12,34,53).stream().max((n1,n2) -> Integer.compare(n1,n2)).get()
List.of(23,12,34,53).stream().min((n1,n2) -> Integer.compare(n1,n2)).get()
List.of(23,12,34,53).stream().filter(e -> e%2==1).forEach(e -> System.out.println(e))
List.of(23,12,34,53).stream().filter(e -> e%2==1).collect(Collectors.toList())
List.of(23,12,34,53).stream().filter(e -> e%2==0).collect(Collectors.toList())
IntStream.range(1,11).map(e -> e * e)
List.of(23,12,34,53).stream().filter(e -> e%2==0).collect(Collectors.toList())
IntStream.range(1,10).map(e -> e * e)
IntStream.range(1,10).map(e -> e * e).boxed().collect(Collectors.toList())
IntStream.range(1,11).map(e -> e * e).boxed().collect(Collectors.toList())
List.of(23,45,67,12).stream().filter(n -> n%2==0).max( (n1,n2) -> Integer.compare(n1,n2) )
$39.get()
$39.isPresent()
List.of(23,45,67).stream().filter(n -> n%2==0).max( (n1,n2) -> Integer.compare(n1,n2) )
$42.isPresent()
$42.orElse(0)
$42.orElse(0)
List.of(23,45,67).stream().filter(n -> n%2==0).max( (n1,n2) -> Integer.compare(n1,n2) ).orElse(0)
List.of(23,45,67,34).stream().filter(n -> n%2==0).max( (n1,n2) -> Integer.compare(n1,n2) ).orElse(0)
```


### /14-FunctionalProgramming/src/com/in28minutes/functionalprogramming/FPNumberRunner.java

```java
package com.in28minutes.functionalprogramming;

import java.util.List;

public class FPNumberRunner {

	public static void main(String[] args) {
		List<Integer> numbers = List.of(4,6,8,13,3,15);
		
		//Exercise - Print squares of first 10 numbers!
		//Clue - IntStream.range(1,10)
		
		//List.of("Apple", "Ant", "Bat").stream()
		//Map all of these to lowercase and print them

		//List.of("Apple", "Ant", "Bat").stream()
		//Print the length of each element

		/*
		numbers.stream()
				.forEach( element ->System.out.println(element));*/
		
		int sum = fpSum(numbers);
			
		System.out.println(sum);

	}

	private static int fpSum(List<Integer> numbers) {
		return numbers.stream()
				.reduce(0, 
					(number1, number2) ->  number1 + number2);
	}

	private static int normalSum(List<Integer> numbers) {
		int sum = 0;
		for(int number:numbers) {
			sum += number; 
		}
		return sum;
	}

}
```


### /14-FunctionalProgramming/src/com/in28minutes/functionalprogramming/FunctionalProgrammingRunner.java

```java
package com.in28minutes.functionalprogramming;

import java.util.List;

public class FunctionalProgrammingRunner {

	public static void main(String[] args) {
		List<String> list = List.of("Apple", "Bat", "Cat",
				"Dog");
		printWithFPWithFiltering(list);

	}

	private static void printBasic(List<String> list) {
		for (String string : list) {
			System.out.println(string);
		}
	}

	private static void printBasicWithFiltering(
			List<String> list) {
		for (String string : list) {
			if (string.endsWith("at")) {
				System.out.println(string);
			}
		}
	}

	private static void printWithFP(List<String> list) {
		list.stream().forEach(element -> System.out
				.println("element - " + element));
	}
	
	private static void printWithFPWithFiltering(List<String> list) {
		list.stream()
				.filter(element -> element.endsWith("at"))
			.forEach(element -> System.out.println("element - " + element));
	}

}
```


### /14-FunctionalProgramming/src/com/in28minutes/functionalprogramming/LambdaBehindTheScreensRunner.java

```java
package com.in28minutes.functionalprogramming;

import java.util.List;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;

class EvenNumberPredicate implements Predicate<Integer> {

	@Override
	public boolean test(Integer number) {
		return number%2 == 0;
	}
	
}

class SystemOutConsumer implements Consumer<Integer> {

	@Override
	public void accept(Integer number) {
		System.out.println(number);
	}
	
}

class NumberSquareMapper implements Function<Integer, Integer> {

	@Override
	public Integer apply(Integer number) {
		return number * number;
	}
	
}

public class LambdaBehindTheScreensRunner {
	
	

	public static void main(String[] args) {

		List.of(23,43,34,45,36,48).stream()
		.filter(n -> n%2 ==0)
		.map(n -> n * n)
		.forEach(e -> System.out.println(e));

		List.of(23,43,34,45,36,48).stream()
		.filter(new EvenNumberPredicate())
		.map(new NumberSquareMapper())
		.forEach(new SystemOutConsumer());

		//.map(n -> n * n)
		//<R> Stream<R> map(Function<? super T, ? extends R> mapper);
		// R apply(T t);
		
		//.filter(new EvenNumberPredicate())
		//Stream<T> filter(Predicate<? super T> predicate);
		//boolean test(T t);
		
		//.forEach(e -> System.out.println(e));
		//Consumer<? super T> action
		//void accept(T t);
		
		//1.Storing functions in variables
		//2.Passing functions to methods <=
		//3.Returning functions from methods
		
		Predicate<? super Integer> evenPredicate = createEvenPredicate();
		Predicate<? super Integer> oddPredicate = n -> n%2 ==1;
		
		List.of(23,43,34,45,36,48).stream()
				.filter(evenPredicate)
				.map(n -> n * n)
				.forEach(e -> System.out.println(e));
	}

	private static Predicate<? super Integer> createEvenPredicate() {
		return n -> n%2 ==0;
	}

}
```


### /14-FunctionalProgramming/src/com/in28minutes/functionalprogramming/MethodReferencesRunner.java

```java
package com.in28minutes.functionalprogramming;

import java.util.List;

public class MethodReferencesRunner {

	public static void print(Integer number) {
		System.out.println(number);
	}

	public static void main(String[] args) {
		List.of("Ant", "Bat", "Cat", "Dog", "Elephant")
				.stream().map(s -> s.length())
				.forEach(s -> MethodReferencesRunner
						.print(s));

		List.of("Ant", "Bat", "Cat", "Dog", "Elephant")
				.stream().map(String::length)
				.forEach(MethodReferencesRunner::print);

		List.of(23,45,67,34).stream()
				.filter(n -> n%2==0)
				.max( (n1,n2) -> Integer.compare(n1,n2) )
				.orElse(0);
		
		Integer max = List.of(23, 45, 67, 34).stream()
				.filter(MethodReferencesRunner::isEven)
				.max(Integer::compare)
				.orElse(0);
		
		System.out.println(max);
	}

	public static boolean isEven(Integer number) {
		return number % 2 == 0;
	}

}
```




# /15-
ThreadsAndConcurrency

## Steps
- Step 01 - Introduction to Threads and MultiThreading - Need for Threads
- Step 02 - Creating a Thread for Task1 - Extending Thread Class
- Step 03 - Creating a Thread for Task2 - Implement Runnable Interface
- Step 04 - Theory - States of a Thread
- Step 05 - Placing Priority Requests for Threads
- Step 06 - Communication between Threads - join method
- Step 07 - Thread utility methods and synchronized keyword - sleep, yield
- Step 08 - Need for Controlling the Execution of Threads
- Step 09 - Introduction to Executor Service 
- Step 10 - Executor Service - Customizing number of Threads
- Step 11 - Executor Service - Returning a Future from Thread using Callable
- Step 12 - Executor Service - Waiting for completion of multiple tasks using invokeAll
- Step 13 - Executor Service - Wait for only the fastest task using invokeAny
- Step 14 - Threads and MultiThreading - Conclusion

## Code Examples

### /15-
ThreadsAndConcurrency/src/CallableRunner.java

```java
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

class CallableTask implements Callable<String> {
   
   private String name;

   public CallableTask(String name) {
      this.name = name;
   }
   
   @Override
   public String call() throws Exception {
      Thread.sleep(1000);
      return "Hello " + name;
   }
   
}

public class CallableRunner {

   public static void main(String[] args) throws InterruptedException, ExecutionException {
      ExecutorService executorService = Executors.newFixedThreadPool(1);
      
      Future<String> welcomeFuture = 
            executorService.submit(new CallableTask("in28Minutes"));
      
      System.out.print("\n new CallableTask(\"in28Minutes\") executed");
      
      String welcomeMessage = welcomeFuture.get();
      
      System.out.println(welcomeMessage);
      
      System.out.print("\n Main completed");

   }

}
```

### /15-
ThreadsAndConcurrency/src/ExecutorServiceRunner.java

```java
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

class Task extends Thread {
	
	private int number;

	public Task(int number) {
		this.number = number;
	}
	
	public void run() { //SIGNATURE
		System.out.print("\nTask " + number + " Started");
		
		for(int i=number*100;i<=number*100 + 99; i++) 
			System.out.print(i + " ");
		
		System.out.print("\nTask" + number +  "Done");
	}
}


public class ExecutorServiceRunner {

	public static void main(String[] args) {
		//ExecutorService executorService = Executors.newSingleThreadExecutor();
		ExecutorService executorService = Executors.newFixedThreadPool(5);
		
		executorService.execute(new Task(1));
		executorService.execute(new Task(2));
		executorService.execute(new Task(3));
		executorService.execute(new Task(4));
		executorService.execute(new Task(5));
		executorService.execute(new Task(6));
		executorService.execute(new Task(7));
				
		executorService.shutdown();

	}

}
```


### /15-
ThreadsAndConcurrency/src/MultipleAnyCallableRunner.java

```java
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class MultipleAnyCallableRunner {

	public static void main(String[] args) throws InterruptedException, ExecutionException {
		ExecutorService executorService = Executors.newFixedThreadPool(3);
		
		List<CallableTask> tasks = List.of(
				new CallableTask("in28Minutes"),
				new CallableTask("Ranga"),
				new CallableTask("Adam"));
		
		String result = executorService.invokeAny(tasks);
		
		System.out.println(result);

		executorService.shutdown();
	}

}
```


### /15-
ThreadsAndConcurrency/src/MultipleCallableRunner.java

```java
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class MultipleCallableRunner {

	public static void main(String[] args) throws InterruptedException, ExecutionException {
		ExecutorService executorService = Executors.newFixedThreadPool(3);
		
		List<CallableTask> tasks = List.of(new CallableTask("in28Minutes"), 
				new CallableTask("Ranga"),  new CallableTask("Adam"));
		
		List<Future<String>> results = executorService.invokeAll(tasks);
		
		for(Future<String> result:results) {
			System.out.println(result.get());
		}

		executorService.shutdown();
	}

}
```


### /15-
ThreadsAndConcurrency/src/ThreadBasicsRunner.java

```java
//extends Thread
//implements Runnable

class Task1 extends Thread {
	
	public void run() { //SIGNATURE
		System.out.print("\nTask1 Started");
		
		for(int i=101;i<=199; i++) 
			System.out.print(i + " ");
		
		System.out.print("\nTask1 Done");
	}
}

class Task2 implements Runnable {

	@Override
	public void run() {
		System.out.print("\nTask2 Started");
		
		for(int i=201;i<=299; i++) 
			System.out.print(i + " ");
		
		System.out.print("\nTask2 Done");
		
		
	}
	
}


public class ThreadBasicsRunner {

	public static void main(String[] args) throws InterruptedException {

		//• NEW;
		//• RUNNABLE;
		//• RUNNING;
		//• BLOCKED/WAITING;
		//• TERMINATED/DEAD;
		
		//Task1 - 101 to 199
		System.out.print("\nTask1 Kicked Off");
		Task1 task1 = new Task1();
		task1.setPriority(1);
		task1.start(); //task1.run();
		
		System.out.print("\nTask2 Kicked Off");
		
		Task2 task2 = new Task2();
		Thread task2Thread = new Thread(task2);
		task2Thread.setPriority(10);
		task2Thread.start();	
	
		task1.join();
		task2Thread.join();
		
		System.out.print("\nTask3 Kicked Off");
		
		//Task3
		for(int i=301;i<=399; i++) 
			System.out.print(i + " ");
		
		System.out.print("\nTask3 Done");
		
		System.out.print("\nMain Done");
	}
}
```


# 16-ExceptionHandling

## Steps
- Step 01 - Introduction to Exception Handling - Your Thought Process during Exception Handling
- Step 02 - Basics of Exceptions - NullPointerException and StackTrace
- Step 03 - Basics of Handling Exceptions - try and catch
- Step 04 - Basics of Handling Exceptions - Exception Hierarchy, Matching and Catching Multiple Exceptions
- Step 05 - Basics of Handling Exceptions - Need for finally
- Step 06 - Basics of Handling Exceptions - Puzzles
- Step 07 - Checked Exceptions vs Unchecked Exceptions - An Example
- Step 08 - Hierarchy of Errors and Exceptions - Checked and Runtime
- Step 09 - Throwing an Exception - Currencies Do Not Match Runtime Exception
- Step 10 - Throwing a Checked Exception - Throws in method signature and handling
- Step 11 - Throwing a Custom Exception - CurrenciesDoNotMatchException
- Step 12 - Write less code with Try with Resources - New Feature in Java 7
- Step 13 - Basics of Handling Exceptions - Puzzles 2
- Step 14 - Exception Handling - Conclusion with Best Practices
## Code Examples

### /16-ExceptionHandling/src/com/in28minutes/exceptionhandling/CheckedExceptionRunner.java

```java
package com.in28minutes.exceptionhandling;

public class CheckedExceptionRunner {
	
	public static void main(String[] args) {
	/*	try {
			someOtherMethod();
			Thread.sleep(2000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}*/
		//someOtherMethod1();
		someOtherMethod2();

	}
	
	private static void someOtherMethod2() throws RuntimeException{
		
	}
	
	private static void someOtherMethod() throws InterruptedException{
		Thread.sleep(2000);
	}

}
```


### /16-ExceptionHandling/src/com/in28minutes/exceptionhandling/ExceptionHandlingRunner.java

```java
package com.in28minutes.exceptionhandling;

public class ExceptionHandlingRunner {

	public static void main(String[] args) {
		method1();
		System.out.println("Main Ended");
	}

	private static void method1() {
		method2();
		System.out.println("Method1 Ended");
	}

	private static void method2() {
		String str = null;
		str.length();
		System.out.println("Method2 Ended");
	}
}
```


### /16-ExceptionHandling/src/com/in28minutes/exceptionhandling/ExceptionHandlingRunner2.java

```java
package com.in28minutes.exceptionhandling;

public class ExceptionHandlingRunner2 {

	public static void main(String[] args) {
		method1();
		System.out.println("Main Ended");
	}

	private static void method1() {
		method2();
		System.out.println("Method1 Ended");
	}

	private static void method2() {
		try {
			//String str = null;
			//str.length();
			int[] i = {1,2};
			int number = i[3];
			System.out.println("Method2 Ended");
		} catch (NullPointerException ex) {
			System.out.println("Matched NullPointerException");
			ex.printStackTrace();
		} catch (ArrayIndexOutOfBoundsException ex) {
			System.out.println("Matched ArrayIndexOutOfBoundsException");
			ex.printStackTrace();
		} catch (Exception ex) {
			System.out.println("Matched Exception");
			ex.printStackTrace();
		}
	}
}
```


### /16-ExceptionHandling/src/com/in28minutes/exceptionhandling/FinallyRunner.java

```java
package com.in28minutes.exceptionhandling;

import java.util.Scanner;

public class FinallyRunner {

	public static void main(String[] args) {
		
		Scanner scanner = null;

		try {
			scanner = new Scanner(System.in);
			int[] numbers = { 12, 3, 4, 5 };

			int number = numbers[21];

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			System.out.println("Before Scanner Close");
			if(scanner!=null) {
				scanner.close();
			}
		}
		
		System.out.println("Just before closing out main");
	}

}
```


### /16-ExceptionHandling/src/com/in28minutes/exceptionhandling/ThrowingExceptionRunner.java

```java
package com.in28minutes.exceptionhandling;

class Amount {
	private String currency;
	private int amount;
	
	public Amount(String currency, int amount) {
		super();
		this.currency = currency;
		this.amount = amount;
	}
	
	public void add(Amount that) throws CurrenciesDoNotMatchException {
		
		if(!this.currency.equals(that.currency)) {
			//throw new Exception("Currencies Don't Match " + this.currency + " & " +that.currency );
			throw new CurrenciesDoNotMatchException("Currencies Don't Match " + this.currency + " & " +that.currency );
		}
		
		this.amount = this.amount + that.amount;
	}
	
	public String toString() {
		return amount + " " + currency; 
	}
}

class CurrenciesDoNotMatchException extends Exception {
	public CurrenciesDoNotMatchException(String msg) {
		super(msg);
	}
}

public class ThrowingExceptionRunner {

	public static void main(String[] args) throws CurrenciesDoNotMatchException {
		Amount amount1 = new Amount("USD", 10);
		Amount amount2 = new Amount("EUR", 20);
		amount1.add(amount2);
		System.out.println(amount1);	
	}

}
```


### /16-ExceptionHandling/src/com/in28minutes/exceptionhandling/TryWithResourcesRunner.java

```java
package com.in28minutes.exceptionhandling;

import java.util.Scanner;

public class TryWithResourcesRunner {

	public static void main(String[] args) {
		try (Scanner scanner = new Scanner(System.in)) {
			int[] numbers = { 12, 3, 4, 5 };
			int number = numbers[21];
		} 
	}

}
```

# 17-Files

## Steps
- Step 01 - List files and folders in Directory with Files list method
- Step 02 - Recursively List and Filter all files and folders in Directory with Step Files walk method and Search with find method
- Step 03 - Read content from a File - Files readAllLines and lines methods
- Step 04 - Writing Content to a File - Files write method
- Step 05 - Files - Conclusion

## Code Examples

### /17-Files/src/files/DirectoryScanRunner.java

```java
package files;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.function.BiPredicate;
import java.util.function.Predicate;

public class DirectoryScanRunner {

	public static void main(String[] args) throws IOException {
		
		Path currentDirectory = Paths.get(".");
		//Files.list(currentDirectory).forEach(System.out::println);
		
		Predicate<? super Path> predicate 
				= path -> String.valueOf(path).contains(".java");
		
		//Files.walk(currentDirectory, 4).filter(predicate).forEach(System.out::println);
		
		BiPredicate<Path, BasicFileAttributes> javaMatcher 
		= (path,attributes) -> String.valueOf(path).contains(".java");

		BiPredicate<Path, BasicFileAttributes> directoryMatcher 
		= (path,attributes) -> attributes.isDirectory();

		
		Files.find(currentDirectory, 4, directoryMatcher )
							.forEach(System.out::println);
		     
	}

}
```


### /17-Files/src/files/FileReadRunner.java

```java
package files;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;

public class FileReadRunner {

	public static void main(String[] args) throws IOException {
		Path pathFileToRead = Paths.get("./resources/data.txt");
		
		//List<String> lines = Files.readAllLines(pathFileToRead);
		//System.out.println(lines);
		
		Files.lines(pathFileToRead)
			.map(String::toLowerCase)
			.filter(str -> str.contains("a"))
			.forEach(System.out::println);
		
	}

}
```


### /17-Files/src/files/FileWriteRunner.java

```java
package files;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;

public class FileWriteRunner {

	public static void main(String[] args) throws IOException {
		Path pathFileToWrite = Paths.get("./resources/file-write.txt");
		
		List<String> list = 
					List.of("Apple", "Boy", "Cat", "Dog", "Elephant");
		
		Files.write(pathFileToWrite, list);
	
		
	}

}
```

### /17-Files/resources/data.txt

```
123,122
jljlfsadf
Apple
Bat
Cat

```


### /17-Files/resources/file-write.txt

```
Apple
Boy
Cat
Dog
Elephant

```

# 18-ConcurrencyLocksAtomicityAndCollections

## Steps
- Step 01 - Getting started with Synchronized
- Step 02 - Problem with Synchronized - Less Concurrency
- Step 03 - Enter Locks with ReEntrantLock
- Step 04 - Introduction to Atomic Classes - AtomicInteger
- Step 05 - Need for ConcurrentMap
- Step 06 - Implementing an example with ConcurrentHashMap
- Step 07 - ConcurrentHashMap uses different locks for diferrent regions
- Step 08 - CopyOnWrite Concurrent Collections - When reads are more than writes
- Step 09 - Conclusion

## Code Examples

### /src/com/in28minutes/concurrency/BiCounter.java

```java
package com.in28minutes.concurrency;

public class BiCounter {
  private int i = 0;
  private int j = 0;
  
  synchronized public void incrementI() {
    i++; 
    //get i
    //increment  
    //set i
  }

  public int getI() {
    return i;
  }
  
  synchronized public void incrementJ() {
    j++; 
    //get j
    //increment  
    //set j
  }

  public int getJ() {
    return j;
  }

}
```
### /src/com/in28minutes/concurrency/BiCounterWithAtomicInteger.java

```java
package com.in28minutes.concurrency;

import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class BiCounterWithAtomicInteger {
  private AtomicInteger i = new AtomicInteger();
  private AtomicInteger j = new AtomicInteger();
    
  public void incrementI() {    
    i.incrementAndGet();
  }

  public int getI() {
    return i.get();
  }
  
  public void incrementJ() {
    j.incrementAndGet(); 
  }

  public int getJ() {
    return j.get();
  }

}
```
### /src/com/in28minutes/concurrency/BiCounterWithLock.java

```java
package com.in28minutes.concurrency;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class BiCounterWithLock {
  private int i = 0;
  private int j = 0;
  
  Lock lockForI = new ReentrantLock();
  Lock lockForJ = new ReentrantLock();
  
  public void incrementI() {    
    lockForI.lock();//Get Lock For I 
    i++;
    lockForI.unlock();
    //Release Lock For I
  }

  public int getI() {
    return i;
  }
  
  public void incrementJ() {
    lockForJ.lock();//Get Lock For J
    j++; 
    lockForJ.unlock();//Release Lock For J
  }

  public int getJ() {
    return j;
  }

}
```
### /src/com/in28minutes/concurrency/ConcurrencyRunner.java

```java
package com.in28minutes.concurrency;

public class ConcurrencyRunner {

  public static void main(String[] args) {
    Counter counter = new Counter();
    counter.increment();
    counter.increment();
    counter.increment();
    System.out.println(counter.getI());

  }

}
```
### /src/com/in28minutes/concurrency/ConcurrentMapRunner.java

```java
package com.in28minutes.concurrency;

import java.util.Hashtable;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.LongAdder;

public class ConcurrentMapRunner {

  public static void main(String[] args) {
    ConcurrentMap<Character, LongAdder> occurances = new ConcurrentHashMap<>();
    
    String str = "ABCD ABCD ABCD";

    for(char character:str.toCharArray()) {
      occurances.computeIfAbsent(character, ch -> new LongAdder()).increment();
    }
    
    System.out.println(occurances);
        

  }

  /*
      Map<Character, LongAdder> occurances = new Hashtable<>();
    
    String str = "ABCD ABCD ABCD";
    for(char character:str.toCharArray()) {
      LongAdder longAdder = occurances.get(character);
      if(longAdder == null) {
        longAdder = new LongAdder();
      }
      longAdder.increment();
      occurances.put(character, longAdder);
    }
    
    System.out.println(occurances);

   */
}
```
### /src/com/in28minutes/concurrency/CopyOnWriteArrayListRunner.java

```java
package com.in28minutes.concurrency;

import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

public class CopyOnWriteArrayListRunner {
  
  //add - copy
  //get

  public static void main(String[] args) {
    List<String> list = new CopyOnWriteArrayList<>();
    
    //Threads - 3
    list.add("Ant");
    list.add("Bat");
    list.add("Cat");
    
    //Threads - 10000
    for(String element:list) {
      System.out.println(element);
    }
    
    // TODO Auto-generated method stub

  }

}
```
### /src/com/in28minutes/concurrency/Counter.java

```java
package com.in28minutes.concurrency;

public class Counter {
  private int i = 0;
  
  synchronized public void increment() {
    i++; 
    //get i
    //increment  
    //set i
  }

  public int getI() {
    return i;
  }
}
```

# 99-TipsAndTricks

## Steps
- Java Tip 01 - Imports and Static Imports
- Java Tip 02 - Blocks
- Java Tip 03 - equals method
- Java Tip 04 - hashcode method
- Java Tip 05 - Class Access Modifiers - public and default
- Java Tip 06 - Method Access Modifiers - public, protected, private and default
- Java Tip 07 - Final classes and Final methods
- Java Tip 08 - Final Variables and Final Arguments
- Java Tip 09 - Why do we need static variables?
- Java Tip 09 - Why do we need static methods?
- Java Tip 10 - Static methods cannot use instance methods or variables
- Java Tip 11 - public static final - Constants
- Java Tip 12 - Nested Classes - Inner Class vs Static Nested Class
- Java Tip 13 - Anonymous Classes
- Java Tip 14 - Why Enum and Enum Basics - ordinal and values
- Java Tip 15 - Enum - Constructor, variables and methods
- Java Tip 16 - Quick look at inbuild Enums - Month, DayOfWeek

## Code Examples

### /src/com/in28minutes/tips/access/package1/ClassAccessModifiers.java

```java
package com.in28minutes.tips.access.package1;


//public, protected, (default), private
public class ClassAccessModifiers {

  public static void main(String[] args) {
    // TODO Auto-generated method stub
    ClassAccessModifiers c = new ClassAccessModifiers();

  }

}
```
### /src/com/in28minutes/tips/access/package1/ExampleClass.java

```java
package com.in28minutes.tips.access.package1;

public class ExampleClass {
  public void publicMethod() {}
  protected void protectedMethod() {}
  private void privateMethod() {}
  void defaultMethod() {}
  
  public static void main(String[] args) {
    ExampleClass exampleClass = new ExampleClass();
    exampleClass.privateMethod();
    exampleClass.protectedMethod();
    exampleClass.publicMethod();
    exampleClass.defaultMethod();
  }
}
```
### /src/com/in28minutes/tips/access/package1/MethodAccessRunnerInsideSamePackage.java

```java
package com.in28minutes.tips.access.package1;

public class MethodAccessRunnerInsideSamePackage {

  public static void main(String[] args) {
    // TODO Auto-generated method stub
    ExampleClass exampleClass = new ExampleClass();
    //exampleClass.privateMethod();
    exampleClass.protectedMethod();
    exampleClass.publicMethod();
    exampleClass.defaultMethod();

  }

}
```
### /src/com/in28minutes/tips/access/package2/ClassAccessModifiersRunnerInOtherPackage.java

```java
package com.in28minutes.tips.access.package2;

import com.in28minutes.tips.access.package1.ClassAccessModifiers;

//public, protected, (default), private
public class ClassAccessModifiersRunnerInOtherPackage {

  public static void main(String[] args) {
    ClassAccessModifiers c = new ClassAccessModifiers();
  }

}
```
### /src/com/in28minutes/tips/access/package2/MethodAccessRunnerInDifferentPackage.java

```java
package com.in28minutes.tips.access.package2;

import com.in28minutes.tips.access.package1.ExampleClass;

public class MethodAccessRunnerInDifferentPackage {

  public static void main(String[] args) {
    // TODO Auto-generated method stub
    ExampleClass exampleClass = new ExampleClass();

    //exampleClass.privateMethod();
    //exampleClass.protectedMethod();
    exampleClass.publicMethod();
    //exampleClass.defaultMethod();

  }

}
```
### /src/com/in28minutes/tips/anonymous/AnonymousClassRunner.java

```java
package com.in28minutes.tips.anonymous;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class AnonymousClassRunner {
  
  public static void main(String[] args) {
    List<String> animals = new ArrayList<String>(
        List.of("Ant", "Cat", "Ball", "Elephant"));
    
    Comparator<String> lengthComparator = new Comparator<String>() {
      @Override
      public int compare(String str1, String str2) {
        return Integer.compare(str1.length(), str2.length());
      }
    };
    
    Collections.sort(animals, 
        lengthComparator
    );
    System.out.println(animals);

  }

}
```
### /src/com/in28minutes/tips/blocks/BlocksRunner.java

```java
package com.in28minutes.tips.blocks;

public class BlocksRunner {
  public static final int SECONDS_IN_MINUTE = 60;
  public static final int MINUTES_IN_HOUR = 60;
  public static final int HOURS_IN_DAY = 24;
  public static final int SECONDS_IN_DAY 
    = SECONDS_IN_MINUTE * MINUTES_IN_HOUR * HOURS_IN_DAY;
  
  public static void main(String[] args) {
    //System.out.print(Integer.MIN_VALUE);
    System.out.print(SECONDS_IN_DAY);
    
    //System.out.print("main");
    
    {
      int i;
      //System.out.print("3>2");
        //System.out.print("3>2");
    }
    
    //System.out.print(i); 

  }

}
```
### /src/com/in28minutes/tips/eclipse/DummyForTest.java

```java
package com.in28minutes.tips.eclipse;

import java.util.ArrayList;
import java.util.List;

public class DummyForTest {

  public void doSomething() {
    List list = new ArrayList();
  }

}
```
### /src/com/in28minutes/tips/eclipse/EclipseTipsAndTricks.java

```java
package com.in28minutes.tips.eclipse;

import java.math.BigDecimal;

//PAIR PROGRAMMING

class TestBean {
  private int i; //i is awesome
  private String str;
  
  
  
  public TestBean() {
    /*
     fsadjflkas
     fskljdfalsk
     */
    super();  
  }
  
  public TestBean(int i, String str) {
    super();
    this.i = i;
    this.str = str;
  }
  /* (non-Javadoc)
   * @see java.lang.Object#hashCode()
   */
  @Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + i;
    return result;
  }
  /* (non-Javadoc)
   * @see java.lang.Object#equals(java.lang.Object)
   */
  @Override
  public boolean equals(Object obj) {
    if (this == obj) {
      return true;
    }
    if (obj == null) {
      return false;
    }
    if (getClass() != obj.getClass()) {
      return false;
    }
    TestBean other = (TestBean) obj;
    if (i != other.i) {
      return false;
    }
    return true;
  }
  /**
   * @return the i
   */
  public int getI() {
    return i;
  }
  /**
   * @param i the i to set
   */
  public void setI(int i) {
    this.i = i;
  }
  /**
   * @return the str
   */
  public String getStr() {
    return str;
  }
  /**
   * @param str the str to set
   */
  public void setStr(String str) {
    this.str = str;
  }
  
  
  
}

class Test implements Comparable<String> {

  @Override
  public int compareTo(String arg0) {
    return 0;
  }
  
}

public class EclipseTipsAndTricks {
  
  public static void main(String[] args) throws InterruptedException {
    
    DummyForTest dt = new DummyForTest();
    dt.doSomething();
    BigDecimal bd = new BigDecimal(25);
    Thread.sleep(returnSomething());
  }

  private static int returnSomething() {
    return 1000 * 45 * 456;
  }

}
```
### /src/com/in28minutes/tips/enums/EnumRunner.java

```java
package com.in28minutes.tips.enums;

import java.util.Arrays;

public class EnumRunner {

  public static void main(String[] args) {
    Season season = Season.FALL;

    Season season1 = Season.valueOf("WINTER");
    System.out.println(season1);
    System.out.println(Season.SPRING.ordinal());
    System.out.println(Season.SPRING.getValue());

    System.out
        .println(Arrays.toString(Season.values()));

  }

}
```
### /src/com/in28minutes/tips/enums/Season.java

```java
package com.in28minutes.tips.enums;
public enum Season {
  SPRING(4), SUMMER(1), WINTER(2), FALL(3) ;
  
  private int value;
  
  private Season(int value) {
    this.value = value;
  }

  public int getValue() {
    return value;
  }
  
  
  //0,1,2,3
}
```
### /src/com/in28minutes/tips/equals/EqualsRunner.java

```java
package com.in28minutes.tips.equals;

class Client {
  private int id;

  public Client(int id) {
    super();
    this.id = id;
  }

  @Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + id;
    return result;
  }

  @Override
  public boolean equals(Object that) {
    if (this == that)
      return true;
    
    if (that == null)
      return false;
    if (getClass() != that.getClass())
      return false;
    Client other = (Client) that;
    if (id != other.id)
      return false;
    return true;
  }
  
  //equals
  //hashcode
  
  
  
}

public class EqualsRunner {

  public static void main(String[] args) {
    Client c1 = new Client(1);
    Client c2 = new Client(1);
    Client c3 = new Client(2);
    System.out.println(c1.equals(c2));
    System.out.println(c1.equals(c3));
    
    
  }

}
```
### /src/com/in28minutes/tips/imports/ImportsRunner.java

```java
package com.in28minutes.tips.imports;

//import java.lang.*; //DEFAULT
import java.math.BigDecimal;
import java.util.ArrayList;
//import java.util.Collections;

import static java.lang.System.out;
import static java.util.Collections.*;

public class ImportsRunner {

  public static void main(String[] args) {
    
    out.println("IMports");
    out.println("Static Imports");
    
    sort(new ArrayList<String>());
    
    BigDecimal db = null;

  }

}
```
### /src/com/in28minutes/tips/nonaccess/package1/FinalNonAccessModifierRunner.java

```java
package com.in28minutes.tips.nonaccess.package1;

final class FinalClass {
  
}

//class SomeClass extends FinalClass{
//}

class SomeClass {
  final public void doSomething() {}
  public void doSomethingElse(final int arg) {
    //arg = 6;
    
  }
}

class ExtendingClass extends SomeClass {
  //public void doSomething() {}
}

public class FinalNonAccessModifierRunner {
  
  public static void main(String[] args) {
    final int i;
    i=5;
    
    //i = 7;

  }

}
```
### /src/com/in28minutes/tips/nonaccess/package1/StaticModifierRunner.java

```java
package com.in28minutes.tips.nonaccess.package1;

class Player{
  private String name;
  
  private static int count = 0;
  
  public Player(String name) {
    super();
    this.name = name;
    count++;
  }

  static public int getCount() {
    return count;
  }

  public String getName() {
    System.out.println(count);
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }
  
  
}

public class StaticModifierRunner {
  
  public static void main(String[] args) {
    Player player1 = new Player("Ronaldo");
    
    System.out.println(Player.getCount());
    
    Player player2 = new Player("Federer");
    
    System.out.println(Player.getCount());
  }

}
```
---