java KeyListener ActionListener 一起添加。哪里错啦？

import java.awt.*;
import java.awt.event.*;

public class TestK {
public static void main(String[] args) {
new KFrame().launchFrame();
}
}

class KFrame extends Frame {
Label lab;
TextField tf;
Button u,d,l,r;
Panel p;
public void launchFrame() {
setBounds(100,100,200,200);
lab = new Label("");
tf = new TextField("",10);
p = new Panel();
p.add(lab);
p.add(tf);
u = new Button("Up");
d = new Button("Down");
l = new Button("Left");
r = new Button("Right");
u.addActionListener(new ButtonMonitor());
d.addActionListener(new ButtonMonitor());
l.addActionListener(new ButtonMonitor());
r.addActionListener(new ButtonMonitor());

add(u, BorderLayout.NORTH);
add(d, BorderLayout.SOUTH);
add(r, BorderLayout.EAST);
add(l, Borde

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