— Scott McNealy, Sun Microsystems Chairman, President and ceo

class MyGui implements ActionListener {
// declare a bunch of instance variables here
public void go() {
// build gui
colorButton = new JButton();
labelButton = new JButton();
colorButton.addActionListener(this);
labelButton.addActionListener(this);
// more gui code here ...
}
public void actionPerformed(ActionEvent event) {
if (event.getSource() == colorButton) {
frame.repaint();
} else {
label.setText(“That hurt!”);
}
}
}
Query the event object 
to find out which button 
actually fired it, and use 
that to decide what to do.
But this is impossible!

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374
 
chapter 12
3
option three
Create two separate ActionListener classes
Flaw: these classes won’t have access to the variables they need 
to act on, ‘frame’ and ‘label’.
You could fix it, but you’d have to give each of the 
listener classes a reference to the main GUI class, so that inside the actionPerformed() 
methods the listener could use the GUI class reference to access the variables of the GUI 
class. But that’s breaking encapsulation, so we’d probably need to make getter methods 
for the gui widgets (getFrame(), getLabel(), etc.). And you’d probably need to add a 
constructor to the listener class so that you can pass the GUI reference to the listener at 
the time the listener is instantiated. And, well, it gets messier and more complicated.
There has got to be a better way!
class MyGui {
JFrame frame;
JLabel label;
void gui() {
// code to instantiate the two listeners and register one