Calling equals(""); by itself compiles and runs

Question

I've noticed that calling equals(""); in a method of a class is not generating any error within Eclipse. I've never seen .equals called without something like string1.equals(string2);.

package voodoo;

public class Equals {

    public void method(){
        equals("");
    }

}

What's going on here and when would calling equals() by itself ever be used?

If I put that into a JUnit to test, it runs and passes.

Answer 1

equals that you are calling is Object's equals method, which can be called on this reference without specifying it explicitly. In other words, your call is equivalent to

this.equals("");

This is perfectly valid, although a well-behaved implementation must always return false. Note that the return value is ignored, which is legal as well.

You can see what's going on by overriding equals with something that prints a message, as a matter of an experiment:

public class Equals {

    public void method(){
        equals("");
    }
    @Override
    public boolean equals(Object other) {
        System.out.println("I am being compared to '"+other+"'");
        return super.equals(other);
    }
}