Reverse String's First And Last Character

package week3;

import java.util.Scanner;

public class Question2 {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        String s1;

        do {

            System.out.println("Enter a string: ");
            s1 = input.nextLine();

            System.out.println("Your string is: " + s1);

            StringBuffer s2 = new StringBuffer(s1);

            char temp = s2.charAt(0);

            s2.setCharAt(0, s2.charAt(s2.length()-1));
            s2.setCharAt(s2.length()-1, temp);

            String s3 = s2.toString();

            System.out.println("Your new string is: " + s3);

        }while(!"quit".equals(s1));
    }
}