大家帮忙 ，一个小问题

[yangyinbo]

import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class MyCanvas implements KeyListener,MouseListener{
Canvas c; String s;
public static void main(String args[]){
Frame f=new Frame("CanvasTest");
MyCanvas mc=new MyCanvas();
mc.c=new Canvas();
f.add(mc.c,"Center");
f.setSize(200,200);
mc.c.addMouseListener(mc);
mc.c.addKeyListener(mc);
f.setVisible(true);
}
public void mouseClicked(MouseEvent ev){
c.requestFocus();
}
public void KeyTyped(KeyEvent ev){
s+=ev.getKeyChar();
c.getGraphics().drawString(s,0,20);
}
public void keyPressed(KeyEvent ev){}
public void keyReleased(KeyEvent ev){}
public void mousePressed(MouseEvent ev){}
public void mouseReleased(MouseEvent ev){}
public void mouseEntered(MouseEvent ev){}
public void mouseExited(MouseEvent ev){}
}


报MyCavans不是抽象的。未覆盖java.awt.event.keylistener中的抽象方法