高手帮忙用Java设计个计算器程序！

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

public class CalcAppDemo extends Frame{
private TextField t_result;
private Panel p_main; //主面板
private Panel p_num; //数字面板
private Panel p_oper; //操作符面板
private Panel p_show; //显示面板
private Button b_num[]; //数字按钮
private Button b_oper[]; //操作符面板

public CalcAppDemo(String title){
setTitle(title);
t_result = new TextField("0.0", 21);
p_main = new Panel();
p_num = new Panel();
p_oper = new Panel();
p_show = new Panel();
p_main.setLayout(new BorderLayout());
p_num.setLayout(new GridLayout(4, 3, 1, 1));
p_oper.setLayout(new GridLayout(4, 2, 1, 1));

b_num = new Button[12];
for(int i=0; i<9; i++)
{
b_num[i] = new Button(new Integer(i+1).toString());
}
b_num[9] = new Button("0");
b_num[10] = new Button("cls");
b_num[11] = new Button(".");
for(int i=