Java Programs easy way

package java2;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Date;

public class met {

      public static String output1;

      public static void fn(String s) {

            StringBuffer sbuf = new StringBuffer();

            if (s.matches("[0-9]{3}[-]{1}[0-9]{3}[-]{1}[0-9]{4}")) {

                  String s1 = s.replace("-", "");

                  sbuf.append(s1.substring(0, 2));

                  sbuf.append("-");

                  sbuf.append(s1.substring(2, 4));

                  sbuf.append("-");

                  sbuf.append(s1.substring(4, 7));

                  sbuf.append("-");

                  sbuf.append(s1.substring(7, 10));

            }

            output1 = sbuf.toString();

      }

      public static void main(String[] args) {

            fn("123-456-7890");

            System.out.println(output1);

      }

}