3 String classes methods

public class Main
{

    public static void main(String[] args) {


        String s1 = new String("ramesh ");
        String s2 = "bad boy";
        String res = s1.concat(s2);
        System.out.println(res);
        System.out.println(res.length());

        StringBuffer s4 = new StringBuffer("Bad boy");

        System.out.println(s4);
        s4.reverse();
        System.out.println(s4);


        if (s1.equals(s2)){
            System.out.println("S1 and s2 are same");
        }
        else{
            System.out.println("S1 and S2 are not same");
        }
    }
}