Warrior Warrior - 6 months ago 22
Java Question

How are Anonymous (inner) classes used in Java?

What is the use of anonymous classes in Java? Can we say that usage of anonymous class is one of the advantages of Java?

Answer

By an "anonymous class", I take it you mean anonymous inner class.

An anonymous inner class can come useful when making an instance of an object with certain "extras" such as overloading methods, without having to actually subclass a class.

I tend to use it as a shortcut for attaching an event listener:

button.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        // do something
    }
});

Using this method makes coding a little bit quicker, as I don't need to make an extra class that implements ActionListener -- I can just instantiate an anonymous inner class without actually making a separate class.

I only use this technique for "quick and dirty" tasks where making an entire class feels unnecessary. Having multiple anonymous inner classes that do exactly the same thing should be refactored to an actual class, be it an inner class or a separate class.