Question

If I do the following,

final class FooButton extends JButton{
    FooButton(){
        super("Foo");
        addActionListener(new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e){
                // do stuff
            }
        });
    }
}

am I letting the this reference implicitly escape?

Answer 1

Yes, because in the anonymous inner class you could access it like this:

final class FooButton extends JButton {
    Foo() {
        super("Foo");
        addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                FooButton button = FooButton.this;
                // ... do something with the button
            }
        });
    }
}

The code of the anonymous ActionListener could in principle be called and use the FooButton before the FooButton object is fully initialized.