Question

JAVA

Implement a public class method named comparison on a public class Compare that accepts two Object arguments.

It should return 0 if both references are equal.

1 if both objects are equal.

and -1 otherwise.

(SUPER IMPORTANT) Either reference can be null, so you'll need to handle those cases carefully!

Here is what I have so far:

public class Compare {

public static int comparison(Object a, Object b) {

  if (a == null || b == null) {

   return null;

  } else if (a.equals(b)) {

   return 0;

  } else if (a == b) {

   return 1;

  } else {

   return -1;

  }

   

}

  

}

I think I'm off with the null part. Thanks!

Answer 1

I have made few changes to your method. I have also added test code. Please use the following

public class Compare {
  
   public static int comparison(Object a, Object b) {
       if (a == null || b == null) {
           return -1;
       }
       // 0 if both references are equal.
       if (a == b) {
           return 0;
       }
       // 1 if both objects are equal.
       if (a.equals(b)) {
           return 1;
       }   
       // -1 otherwise
       return -1;
      
   }

   public static void main(String[] args) {
       String s1 = new String("abcd");
       String s2 = s1;
       String s3 = new String("abcd");
       String s4 = new String("abcde");
       System.out.println("s1 == s2 : " + comparison(s1,s2));
       System.out.println("s1 == s3 : " + comparison(s1,s3));
       System.out.println("s2 == s3 : " + comparison(s2,s3));
       System.out.println("s1 == s4 : " + comparison(s1,s4));
   }

}

It will produce the following output