Java：用于创建实现接口的类的实例的简写形式

Question

I'd like to use the new operator to create an instance of JPanel that implements ActionListener and directly overrides the actionPerformed method.

I tried

JPanel panel = new JPanel implements ActionListener() {
    @Override
    public void actionPerformed(ActionEvent ae) {
        // ...
    }
};

but that doesn't work because of a syntax error.

Of course I could just define a new class like JPanelWithActionListener and call this one with new , but is there any way to do it in just one line?

Answer 1

That is not possible in Java - there is no anonymous type in Java.

Your code new JPanel implements ActionListener() { /*...*/ }; is equivalent to this code.

class JPanelWithActionListener extends JPanel implements ActionListener {
    @Override
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub
    }
}
JPanel panle = new JPanelWithActionListener();

You want to create a new type JPanelWithActionListener without defining a class (so, that class is anonymous).