Question

Guys I know this question is silly but just to make sure:
Having in my class method:

boolean equals(Document d)
{
//do something
}

I’m overloading this method nor overriding right? I know that this or similiar question will be on upcoming egzam and would be stupid to not get points for such a simple mistake;

Answer 1

You are not even overloading, since the other method is called equals. But if you add that s, you will be overloading equals. Although, to be precise, we talk about overloading if two (or more) methods with the same name but different signature are defined in the same class. In your case, it is trickier, since your equals with its different signature partly hides the original equals. Which is usually a bad thing, because this almost always leads to hard to understand behaviour, thus subtle bugs. Whenever someone calls equals on an instance of your class, depending on the parameter type the call may go to a different implementation of the method.

class Document {
  public boolean equals(Document d)
  {
    //do something
  }
}

Document doc1 = new Document();
Document doc2 = new Document();
String string = new String();

doc1.equals(doc2); // calls Document.equals
doc1.equals(string); // calls Object.equals!

You would be overriding Object.equals if you defined your method with the exact same signature as the original, i.e.

public boolean equals(Object obj) ...

In this case, both of the above calls to equals correctly execute Document.equals.