Review of actionPerformed()

The parameter for actionPerformed() is a reference to an ActionEvent object, a subclass of AWTEvent. When a button is clicked, actionPerformed() is called with a new ActionEvent parameter. So far, we've not used the ActionEvent object. We will do this shortly. Here is the picture:

The registered ActionListener may be the object that contains the button. For small applications, this is an object of a type that is a subclass of JFrame. (In other words, you define a class based on JFrame.) The class contains the button and also implements the ActionListener interface.

In larger applications, the registered listener may be in a class by itself, or be in a JPanel. See the following chapters.