class ProveStringImmutable
              {
              public static void referenceCheck(Object x, Object y) {
              if (x == y) {
              System.out.println("Both pointing to the same reference");
              
              } else {
              System.out.println("Both are pointing to different reference");
              }
              }
              public static void main(String[] args) {
              String st1 = "Java";
              String st2 = "Java";
              System.out.println("\nBefore Modification in st1");
              referenceCheck(st1, st2);
              st1 += "ava";
              System.out.println("After Modification");
              referenceCheck(st1, st2);
              }
              }