Compare two objects with "<" or ">" operators in Java

Question

How to make two objects in Java comparable using "<" or ">" e.g.

MyObject<String> obj1= new MyObject<String>(“blablabla”, 25);
MyObject<String> obj2= new MyObject<String>(“nannaanana”, 17);
if (obj1 > obj2) 
    do something. 

I've made MyObject class header as

public class MyObject<T extends Comparable<T>> implements Comparable<MyObject<T>> and created method Comp but all the gain I got is now I can use "sort" on the list of objects, but how can I compare two objects to each other directly? Is

if(obj1.compareTo(obj2) > 0)
     do something

the only way?

Answer 1

You cannot do operator overloading in Java. This means you are not able to define custom behaviors for operators such as +, >, <, ==, etc. in your own classes.

As you already noted, implementing Comparable and using the compareTo() method is probably the way to go in this case.

Another option is to create a Comparator (see the docs), specially if it doesn't make sense for the class to implement Comparable or if you need to compare objects from the same class in different ways.

To improve the code readability you could use compareTo() together with custom methods that may look more natural. For example:

boolean isGreaterThan(MyObject<T> that) {
    return this.compareTo(that) > 0;
}

boolean isLessThan(MyObject<T> that) {
    return this.compareTo(that) < 0;
}

Then you could use them like this:

if (obj1.isGreaterThan(obj2)) {
    // do something
}