Programming Groovy 2

2.6 Implementing Interfaces

In Groovy we can morph a map or a block of code into interfaces, which lets us implement interfaces with multiple methods quickly. In this section, you’ll see a Java way of implementing interfaces, and then you’ll learn how to take advantage of Groovy’s facilities.

Here’s the all-too-familiar Java code to register an event handler to a Swing ​JButton​. The call to ​addActionListener​ expects an instance that implements the ​ActionListener​ interface. We create an anonymous inner class that implements ​ActionListener​, and we provide the required ​actionPerformed​ method. This method insists on taking ​ActionEvent​ as an argument even though we have no use for it in this example.

// Java code
button.addActionListener( ...