unit1_1_2.java

class unit1_1_2 {
    public static void main(String[] args) {
        // Encounter the String data type, and know that strings are
        // specified using double quotes

        // In Java, a String can be considered as an array of characters, 
        // and the sequence of characters is called a string. 
        String str1 = "Hello World"; 
        System.out.println("str1: " + str1);

        // The above string is equivalent to an array of char as follows:
        char ch[] = {'H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd'};  
        String str2 = new String(ch);

        System.out.println("str2: " + str2);

        // Length of a String is represented by an integer
        System.out.println("Length of str2: " + str2.length());
        System.out.println("char at index 0 of str2: " + str2.charAt(0));
        System.out.println("char at index 1 of str2: " + str2.charAt(1));
        System.out.println("char at index 2 of str2: " + str2.charAt(2));
        System.out.println("char at index 3 of str2: " + str2.charAt(3));
        System.out.println("char at index 4 of str2: " + str2.charAt(4));
        System.out.println("char at index 5 of str2: " + str2.charAt(5));
        System.out.println("char at index 6 of str2: " + str2.charAt(6));
        System.out.println("char at index 7 of str2: " + str2.charAt(7));
        System.out.println("char at index 8 of str2: " + str2.charAt(8));
        System.out.println("char at index 9 of str2: " + str2.charAt(9));
        System.out.println("char at index 10 of str2: " + str2.charAt(10));

        // The size of int in Java is 4 bytes (included a signed bit, i.e. MSB). [MSB-> Most Significant Bit] 
        // 4 bytes: [sign bit]bbbbbbb bbbbbbbb bbbbbbbb bbbbbbbb where b stands for 0 or 1; 
        // Sign bit 0 is +ve, 1 is -ve
        //
        // The range of integer data type is -2^31 to (2^31)-1 (-2147483648 to 2147483647). 
        // Remember that we cannot use negative values for indexing. 
        // The indexing is done within the maximum range. 
        // It means that we cannot store the 2147483648th character. 
        // Therefore, the maximum length of String in Java is 0 to 2147483647. 
        // So, we can have a String with the length of 2,147,483,647 characters, theoretically.
    }
}