Question

Why is this legal?:

public class TwoFrames extends JFrame {
    public TwoFrames() {
        return;
    };
}

And this isn’t (NetBeans IDE saying invalid method declaration; return type required)?:

public class TwoFrames extends JFrame {
    public firstFrame() {
        return;
    };
}

Answer 1

That is a constructor. It is called once the object is initialized. For example:

TwoFrames twoFrames = new TwoFrames();

Unlike regular methods constructors does not return any value. Why should it?

Also, the constructor has to have the same name as the class.

Hope this helps you.