import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JOptionPane;
 
 
public class FocusTest extends JApplet {
 
    JButton button;
 
    public void init() {
        button = new JButton("Ok");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                requestFocusInWindow();
            }
        });
        setLayout(new BorderLayout());
        add(button,BorderLayout.SOUTH);
 
        setFocusable(true);
        addKeyListener(new KeyAdapter() {
            public void keyPressed(KeyEvent e) {
                JOptionPane.showMessageDialog(FocusTest.this, "Key pressed");
            }
 
        });
    }
}