急急急！一个applet程序问题，高手进来看看吧！！

package com.fct.applet;

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

public class Jisuan extends Applet implements ActionListener {
Label prompt;
TextField input1, input2;
Button btn;
public int length, width;
Rect t = new Rect();

public void init() {
prompt = new Label("请输入：");
btn = new Button("计算");
input1 = new TextField(4);
input2 = new TextField(4);
add(prompt);
add(input1);
add(input2);
add(btn);
btn.addActionListener(this);
}

public void actionPerformed(ActionEvent e) {
length = Integer.parseInt(input1.getText());
width = Integer.parseInt(input2.getText());
repaint();
}

public void paint(Graphics g) {
g.drawString("周长是" + t.A(), 10, 50);
g.drawString("面积是" + t.B(), 10, 70);
}

class Rect {