Declaring a new object and calling some of its methods on creation

Question

I happened about this declaration on the internet and found it really interesting. However I don't know what to search for to get more information about it. If you could tell me a bit about this or what to search for...

(the calling of methods on declaration)

 JPanel bluePanel = new JPanel(){{
        setBackground(Color.blue);
        setLocation(220, 10);
        setSize(50, 50);
 }};

`setLocation(220, 10); setSize(50, 50);` Lose whatever you found. It is rubbish code. — Andrew Thompson, May 16 '13 at 12:44

Brian Agnew · Accepted Answer · 2013-05-16T12:45:30.443

You're deriving an anonymous subclass of JPanel and then declaring a initialiser block for it.

Here's the subclass:

new JPanel(){};

Note the braces. And the initaliser is declared within it:

new JPanel() {
 { 
    // static initaliser
 }
};

The derivation of a subclass is simply to allow the initialiser block. This is called double-brace initialisation, and some worry about the abuse of creating an anonymous class simply for this purpose.

See here for more info about the initialiser block.

Declaring a new object and calling some of its methods on creation

1 Answers1