Which method do I have to overwrite in Java to use “>” to compare instances of my class

Question

As far as I understand I can overwrite equals() in Java to handle how my class interacts with == . Which method do I have to overwrite to be define the behavior of

MyClass obj1;
MyClass obj2;
if (obj1 > obj2){
    ...
}

Answer 1

You can't. Java doesn't support custom operator overloading. Overriding equals doesn't affect == . The closest you can get to < is to implement the Comparable interface, which includes a compareTo method. http://docs.oracle.com/javase/7/docs/api/java/lang/Comparable.html

Answer 2

As far as I understand I can overwrite equals() in Java to handle how my class interacts with ==

This is wrong. The explanation is already covered here: How do I compare strings in Java? :

== tests for reference equality.

.equals() tests for value equality.

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To your question:

Unlike C++ or C#, in Java you cannot overload operators.

Instead of using > and < operators you have two options.

1. Make MyClass implement Comparable :

    public MyClass implements Comparable<MyClass> { @Override public int compareTo(MyClass other) { //comparison logic here... } } 

   You will use it like this:

    MyClass obj1 = ...; MyClass obj2 = ...; if (obj1.compareTo(obj2) > 0){ ... } 

2. Create a class that implements Comparator

    public class MyClassComparator implements Comparator<MyClass> { @Override public int compare(MyClass myClass1, MyClass myClass2) { //comparison logic here... } } 

   You will use it like this:

    MyClass obj1 = ...; MyClass obj2 = ...; MyClassComparator comp = new MyClassComparator(); if (comp.compare(obj1, obj2) > 0){ ... }