西子奥的斯7层电梯价格:java程序问题

这是一个时钟程序，运行时为什么说 出现cannot resolve symbol
symbol:bariable lastym
location: class Clock
if<xm!=last||ym!=lastym> //lastym错

请高手指点指点

import java.util.*;
import java.awt.*;
import java.applet.*;
public class Clock extends Applet implements Runnable
{
Thread timer=null;
int lastxs=0,lastys=0,lastxm=0,lastxh=0,lastyh=0;
public void init()
{
setBackground(Color.white);
}
public void paint(Graphics g)
{
int xh,yh,xm,ym,xs,ys,s,m,h,xcenter,ycenter;
Date rightnow=new Date();
String today=rightnow.toLocaleString();
s=rightnow.getSeconds();
m=rightnow.getMinutes();
h=rightnow.getHours();
xcenter=80;
ycenter=80;
xs=(int)(Math.cos(s*3.14f/30-3.14f/2)*45+xcenter);
ys=(int)(Math.sin(s*3.14f/30-3.14f/2)*45+ycenter);
xm=(int)(Math.cos(m*3.14f/30-3.14f/2)*40+xcenter);
ym=(int)(Math.sin(m*3.14f/30-3.14f/2)*40+ycenter);
xh=(int)(Math.cos((h*30+m/2)*3.14f/180-3.14f/2)*30+xcenter);
yh=(int)(Math.sin((h*30+m/2)*3.14f/180-3.14f/2)*30+ycenter);
g.setFont(new Font("TimesRoman",Font.PLAIN,14));
g.setColor(Color.blue);
g.drawArc(xcenter-50,ycenter-50,100,100,0,360);
g.setColor(Color.darkGray);
g.drawString("9",xcenter-45,ycenter+3);
g.drawString("3",xcenter+40,ycenter+3);
g.drawString("12",xcenter-5,ycenter-37);
g.drawString("6",xcenter-3,ycenter+45);
g.setColor(getBackground());
if(xs!=lastxs||ys!=lastys)
{
g.drawLine(xcenter,ycenter,lastxs,lastys);
g.drawString(today,5,150);

}
if(xm!=lastxm||ym!=lastym)
{
g.drawLine(xcenter,ycenter-1,lastxm,lastym);
g.drawLine(xcenter-1,ycenter,lastxm,lastym);

}
if(xh!=lastxh||yh!=lastyh)
{
g.drawLine(xcenter,ycenter-1,lastxh,lastyh);
g.drawLine(xcenter-1,ycenter,lastxh,lastyh);
}
g.setColor(Color.darkGray);
g.drawString(today,5,150);
g.setColor(Color.blue);
g.drawLine(xcenter,ycenter,xs,ys);
g.drawLine(xcenter,ycenter-1,xm,ym);
g.drawLine(xcenter-1,ycenter,xm,ym);
g.drawLine(xcenter,ycenter-1,xh,yh);
g.drawLine(xcenter-1,ycenter,xh,yh);
lastxs=xs;lastys=ys;
lastxm=xm;lastym=ym;
lastxh=xh;lastyh=yh;

}
public void start()
{
if(timer==null)
{
timer=new Thread(this);
timer.start();
}
}
public void stop()
{
timer=null;

}
public void run()
{
while(timer!=null)
{
try
{
Thread.sleep(1000);
}
catch(InterruptedException e){}
repaint();
}
timer=null;
}
public void update(Graphics g)
{
paint(g);
}
}