谁能帮我修改一下，谢谢
代码如下，编译出现提示，但能通过，运行出现错误
package   playgame;

import   java.util.*;
import   javax.swing.*;
import   java.awt.*;
import   java.awt.event.*;

interface   CharacterSource{
public   void   addCharacterListener(CharacterListener   cl);
public   void   removeCharacterListener(CharacterListener   cl);
public   void   nextCharacter();
}

interface   CharacterListener{
public   void   newCharacter(CharacterEvent   ce);
}

class   CharacterEvent{
public   CharacterSource   source;
public   int   character;
public   CharacterEvent(CharacterSource   cs,int   c){
source=cs;
character=c;
}
}

class   CharacterEventHandler{
private   Vector   listeners=new   Vector();

public   void   addCharacterListener(CharacterListener   cl){
listeners.add(cl);
}

public   void   removeCharacterListener(CharacterListener   cl){
listeners.remove(cl);
}

public   void   fireNewCharacter(CharacterSource   source,int   c){
CharacterEvent   ce=new   CharacterEvent(source,c);
CharacterListener[]   cl=(CharacterListener[]   )listeners.toArray(new   CharacterListener[0]);
for(int   i=0;i <cl.length;i++){
cl[i].newCharacter(ce);
}
}
}

class   CharacterDisplayCanvas   extends   JComponent   implements   CharacterListener{
protected   FontMetrics   fm;
protected   char[]   tmpChar=new   char[1];
protected   int   fontHeight;

public   CharacterDisplayCanvas(){
setFont(new   Font( "Monospaced ",Font.BOLD,18));
fm=Toolkit.getDefaultToolkit().getFontMetrics(getFont());
fontHeight=fm.getHeight();
}

public   CharacterDisplayCanvas(CharacterSource   cs){
this();
setCharacterSource(cs);
}

public   void   setCharacterSource(CharacterSource   cs){
cs.addCharacterListener(this);
}

public   Dimension   preferredsize(){
return   new   Dimension(fm.getMaxAscent()+10,fm.getMaxAdvance()+10);
}

public   synchronized   void   newCharacter(CharacterEvent   ce){
tmpChar[0]=(char)ce.character;
repaint();
}

protected   synchronized   void   paintComponent(Graphics   gc){
Dimension   d=getSize();
gc.clearRect(0,0,d.width,d.height);
if(tmpChar[0]==0)return;
int   charWidth=fm.charWidth((int)tmpChar[0]);
gc.drawChars(tmpChar,0,1,(d.width-charWidth)/2,fontHeight);
}
}

class   RandomCharacterGenerator   extends   Thread   implements   CharacterSource{
static   char[]   chars;
static   String   charArray= "abcdefghijklmnopqrstuvwxyz ";
static{
chars=charArray.toCharArray();
}

Random   random;
CharacterEventHandler   handler;

public   RandomCharacterGenerator(){
random=new   Random();
handler=new   CharacterEventHandler();
}

public   int   getPauseTime(){
return   (int)(Math.max(1000,5000*random.nextDouble()));
}

public   void   addCharacterListener(CharacterListener   cl){
handler.addCharacterListener(cl);
}