java 画布清除

我在异常处理的时候画布和文本框的内容不能同时清除。。。哪位高手能帮帮忙啊
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
class Mycanvas extends Canvas
{
int x,y,w,h;
Mycanvas()
{
setBackground(Color.pink);
}
public void setX(int x)
{
this.x=x;
}
public void setY(int y)
{
this.y=y;
}
public void setW(int w)
{
this.w=w;
}
public void setH(int h)
{
this.h=h;
}
public void paint(Graphics g)
{
g.drawRect(x,y,w,h);
}
}
public class hello extends Applet implements ActionListener
{
Mycanvas canvas;
TextField inputX,inputY,inputW,inputH;
Button b;
public void init()
{ canvas=new Mycanvas();
inputX=new TextField(5);
inputY=new TextField(5);
inputW=new TextField(5);
inputH=new TextField(5);

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
class Mycanvas extends Canvas {
int x,y,w,h;
public boolean b = true;
public Mycanvas() {
setBackground(Color.pink);
}
public void setX(int x) {
this.x=x;
}
public void setY(int y) {
this.y=y;
}
public void setW(int w) {
this.w=w;
}
public void setH(int h) {
this.h=h;
}
public void paint(Graphics g) {
if(b) {
g.drawRect(x,y,w,h);
}
}
}
public class windowClick extends Applet implements ActionListener {
Mycanvas canvas;
TextField inputX,inputY,inputW,inputH;
Button b;
boolean bb = false;
public void init() {
canvas=new Mycanvas();
inputX=new TextField(5);
inputY=new TextField(5);