java高手帮我修改一下（急用）

import java.awt.*;
import java.awt.event.*; //加入的事件包
import javax.swing.*;

public class jsq
extends JFrame
implements ActionListener {
//添加的变量
private double arg = 0;
private String op = "=";
private boolean start = true;

JPanel jp = new JPanel();
JPanel jp1 = new JPanel();
JPanel jp2 = new JPanel();
JPanel jp3 = new JPanel();
JPanel jp4 = new JPanel();
JPanel jp5 = new JPanel();
JPanel jp6 = new JPanel();
JPanel jp7 = new JPanel();
JTextField jtf = new JTextField(16);
JButton[] jb = new JButton[18];
String[] st = {
"Backspace", "CE", "7", "8", "9", "/", "4", "5", "6", "*", "1", "2", "3",
"-", "0", ".", "+", "="};
GridLayout glo1 = new GridLayout(6,