Java by API/java.awt.event/FocusAdapter

extends FocusAdapter

 

import java.awt.event.FocusAdapter;
import java.awt.event.FocusEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
public class Main {
  public static void main(String[] argv) throws Exception {
    JButton component = new JButton("a");
    component.addFocusListener(new MyFocusListener());
    
    JFrame f = new JFrame();
    f.add(component);
    f.pack();
    f.setVisible(true);
    
    
  }
}
class MyFocusListener extends FocusAdapter {
  public void focusGained(FocusEvent evt) {
    System.out.println("gained the focus.");
  }
  public void focusLost(FocusEvent evt) {
    System.out.println("lost the focus.");
    boolean isTemporary = evt.isTemporary();
  }
}