Java™ How To Program (Early Objects), Tenth Edition

Registering Events

Every JComponent has an instance variable called listenerList that refers to an object of class event-listenerList (package javax.swing.event). Each object of a JComponent subclass maintains references to its registered listeners in the listenerList. For simplicity, we’ve diagramed listenerList as an array below the JTextField object in Fig. 12.13.

Fig. 12.13 | Event registration for JTextField textField1.

When the following statement (line 43 of Fig. 12.9) executes

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textField1.addActionListener(handler);

a new entry containing a reference to the TextFieldHandler object is placed in textField1 ...