08 Boxed Primitives.md

Boxed Primitives ( Type Wrappers )

• java uses primitive types ( int, float, double, char ) to hold the basic data types.
• using objects for these values would add an unacceptable overhead to even the simplest of calculations.
• despite the performance benefit offered by the primitives, there are times when you will need an object representation. E.x: i. you cannot pass a primitive type by reference to a method. ii. many standard data structures implemented by java operate on objects, you can't use primitives.
• To handle this kind of situation java provides type wrappers, which are classes that encapsulate a primitive type within an object.
• Java provides immutable wrapper classes for all primitive types:

primitives	Wrapper Class
short	Short
byte	Byte
int	Integer
long	Long
char	Character
boolean	Boolean
float	Float
double	Double

    Integer a = Integer.valueOf(5);
    Integer b = 8;
    int c = b.intValue();

• Modern versions of java have included two important features:

AutoBoxing:

• process by which a primitive type is automatically encapsulated ( boxed ) into its equivalent type wrapper whenever an object of that type is needed.

Auto-unboxing:

• process by which the value of a boxed object is automatically extracted ( unboxed ) from a type wrapper when its value is needed.

    Integer num1 = 100; // auto box int to Integer

    int i = num1; // auto unboxing 
    

• Autoboxing and Auto-unboxing happens where the other types are needed.
• for example:

public static void main(String[] args){
    Boolean b = true;
    if(b){
      system.out.println("hello");
    }
}

• Since wrapper Boolean is used inside if condition, it is auto unboxed to primitives and the condition is checked.
• Auto unboxing happens automatically during conditional expression of while, for, or do while loops.

warning: Although using wrapper types is completely fine, it adds an overhead of auto boxing and unboxing, so it is better to use primitives and only use wrappers where the object representation of a primitive type is required.

Boxed Primitive Methods

• Integer.parseInt(), Double.parseDouble()
• compareTo - works the same way as string