Anonymous Inner Class

Anonymous inner class in two statements.

define and instantiate

    ActionListener listener = new ActionListener() {
        public void actionPerformed(ActionEvent event) {
            setVisible(false);
        }
    };

add

    okButton.addActionListener(listener);

Anonymous inner class in one statement.

define, instantiate, and add

    okButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent event) {
            setVisible(false);
        }
    });