Jack.java

public class Jack {
    public static void main(String[] args) {
    /*    String s = "sachin";
        System.out.println(s.concat(" tendulkar"));
        s += " IND" ;
        System.out.println(s);
       s = s+" MI";
        System.out.println(s);
        System.out.println(s.substring(7,10));
        System.out.println(s.substring(7));
        System.out.println(s.length());
        System.out.println(s.replace('n','Z'));
        System.out.println(s.toLowerCase());
        System.out.println(s.toUpperCase());
        System.out.println(s.trim());
        System.out.println(s.indexOf('k'));
        System.out.println(s.indexOf('I'));
        System.out.println(s.lastIndexOf('I'));

        String s1=new String("sachin");

        String s2=s1.toString();

        String s3=s1.toUpperCase();

        String s4=s1.toLowerCase();

        String s5=s1.toUpperCase();

        String s6=s1.toLowerCase();

        System.out.print(s1==s6);//true
        System.out.print(s1==s2);//true
        System.out.print(s1==s3);//false
        System.out.print(s1==s4);//true
        System.out.print(s1==s5);//false

        System.out.print(s3==s6);//false     */

        String s1 = "hello";
        System.out.println(s1.concat(" ").concat("world"));
    }
}