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Confused about ActionListener syntax
Hi,
I'm going through java swing tutorials here, and there's a line I don't understand:
JButton button = new JButton("Click me"); button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { tf.setText("Welcome to swing"); } });
Can someone please explain to me how you can define a method there? I've not come across this sort of definition before. Thanks
Re: Confused about ActionListener syntax
That particular construct is known as an anonymous class. You can specify a class or an interface and it will construct a class in its place. I would advise against using it for very large classes. It can get cumbersome and hard to read.
And as of Java 8 you can use a Lambda expression in place of an anonymous class or class reference.
JButton b = new JButton(); b.addActionListener((event)->System.out.println("Button Pushed")); b.doClick(); // triggers event and prints 'Button Pushed'
Regards,
Jim
dboxall123 (October 5th, 2018)
Re: Confused about ActionListener syntax
Great, I'll read up on anonymous classes and lambda expressions, thanks Jim
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