How to use binary operators "<" and ">" for comparing objects in Java? [duplicate]

Question

Consider having this class in Java:

public class Foo implements Comparable<Foo> {
    private int someValue;

    @Override
    public int compareTo(Foo o) {
        if (this.someValue < o.someValue) {
            return -1;
        } else if (this.someValue == o.someValue) {
            return 0;
        } else {
            return 1;
        }
    }
}

I tried to do this:

Foo foo1 = new Foo(someValue);
Foo foo2 = new Foo(someAnotherValue);
if (foo1 < foo2) {
   // do something
}

But the IDE is giving me an error which is: "Bad operand types for binary operation '<' first type: Foo, second type: Foo"

May you please tell me what is wrong?

Thanks in advance for your help,

You can't. Those operators can only be used with numeric types. Foo is not a numeric type. — Savior
– Savior, Commented Apr 12, 2016 at 21:54
Java (unlike some other languages), does not support operator overloading. — Elliott Frisch
– Elliott Frisch, Commented Apr 12, 2016 at 21:57

rgettman · Accepted Answer · 2016-04-12 21:56:13Z

4

Implementing the Comparable interface is a good first step to being able to compare your objects properly. However, that doesn't allow you to use the < and > comparison operators as if the operators were overloaded. You just need to call your compareTo method.

if (foo1.compareTo(foo2) < 0) {

answered Apr 12, 2016 at 21:56

rgettman

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