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Java Java Data Structures - Retired Organizing Data Comparable

edumorlom
edumorlom
4,073 Points
Posted by edumorlom
edumorlom
4,073 Points

Why did we have to if equal return 0, doesn't the compareTo method already do that?

The compareTo() method returns: -1 1 0 if they are equal.

Why did we have to check for equality in the method when overriding the method and return 0 if true? Doesn't the compareTo method already do that? Im confused.

Here's my code.

@Override
  public int compareTo(Object obj ) {
    BlogPost post = (BlogPost) obj;
    if (equals(post)) { //<-----------changed this to match the video
      return 0;
    }
    return mCreationDate.compareTo(post.getCreationDate()); //Shouldn't this return 1, -1 or 0?
  }

1 Answer

markmneimneh
markmneimneh
14,132 Points

Hello

@Override

Step 1

This line is a simple casting to BlogPost 

BlogPost post = (BlogPost) obj;

Step 2

This block simply say if 'this object' equials post (meaning they both points to same address in memory

if (equals(post)) { //<-----------changed this to match the video

  return 0;

then return 0. there is no point in going any further.

Step 3

Now this next line happen only if the 'if' condition fails. in that case, "this" and Post are not same object.. Hence, we need to use this over-ridden equal method:

return mCreationDate.compareTo(post.getCreationDate()); //Shouldn't this return 1, -1 or 0?

Hope this helps. If this answers your question, please mark question as answered.