Code Samples from the Java Developers Almanac 2000

 component.addFocusListener(new MyFocusListener());
     
 public class MyFocusListener extends FocusAdapter {
   public void focusGained(FocusEvent evt) {
     // The component gained the focus.
   }
   public void focusLost(FocusEvent evt) {
     // The component lost the focus.
   }
 }