大家帮帮我！！（初学）

Question

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;public class Calculator {
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        CalculatorFrame frame=new CalculatorFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.show();
    }    
}class CalculatorFrame extends JFrame{
    public CalculatorFrame(){
        setTitle("Calculator");
        setSize(WIDTH,HEIGHT);
        
        Container contentPane=getContentPane();
        CalculatorPanel panel=new CalculatorPanel();
        contentPane.add(panel);
    }
    public static final int WIDTH=200;
    public static final int HEIGHT=200;
}class CalculatorPanel extends JPanel
{
    public CalculatorPanel()
    {
        setLayout(new BorderLayout());
        
        result=0;
        lastCommand="=";
        start=true;
        
        display=new JTextField("0");
        display.setEditable(false);
        add(display,BorderLayout.NORTH);
        
        ActionListener insert=new InsertAction();
        ActionListener command=new CommandAction();
        
        panel=new JPanel();
        panel.setLayout(new GridLayout(4,4));
        
        addButton("7",insert);
        addButton("8",insert);
        addButton("9",insert);
        addButton("/",command);
        
        addButton("4",insert);
        addButton("5",insert);
        addButton("6",insert);
        addButton("*",command);
        
        addButton("1",insert);
        addButton("2",insert);
        addButton("3",insert);
        addButton("-",command);
        
        addButton("0",insert);
        addButton(".",insert);
        addButton("=",command);
        addButton("+",command);
        
        add(panel,BorderLayout.CENTER);
    }
    
    private void addButton(String label,ActionListener listener)
    {
        JButton button=new JButton(label);
        button.addActionListener(listener);
        panel.add(button);
    }
    
    private class InsertAction implements ActionListener
    {
        public void actionPerformed(ActionEvent event)
        {
            String input=event.getActionCommand();
            if(start)
            {
                display.setText("");
                start=false;
            }
            display.setText(display.getText()+input);
        }
    }
    
    private class CommandAction implements ActionListener
    {
        public void actionPerformed(ActionEvent evt)
        {
            String command=evt.getActionCommand();
            if(start)
            {
                if(command.equals("="))
                {
                    display.setText(command);
                    start=false;
                }
                else
                    lastCommand=command;
            }
            else
            {
                calculate(Double.parseDouble(display.getText()));
                lastCommand=command;
                start=true;
            }
        }
    }
    
    public void calculate(double x)
    {
        if(lastCommand.equals("+")) result+=x;
        else if(lastCommand.equals("-")) result-=x;
        else if(lastCommand.equals("*")) result*=x;
        else if(lastCommand.equals("/")) result/=x;
        else if(lastCommand.equals("=")) result=x;
        display.setText(""+result);
    }
    
    private JTextField display;
    private JPanel panel;
    private double result;
    private String lastCommand;
    private boolean start;
}这是代码不完善自己看看吧，功能都实现了

Answer 1

好像有个方法可以从事件中判断是否双击鼠标右键，方法名忘了，可参考清华的《JFC核心》。

Answer 2

谢谢楼上的：）有个地方不是太明白能结实一下吗？ 谢谢！private class CommandAction implements ActionListener
    {
        public void actionPerformed(ActionEvent evt)
        {
            String command=evt.getActionCommand();
            if(start)
            {
                if(command.equals("="))
                {
                    display.setText(command);
                    start=false;
                }
                else
                    lastCommand=command;
            }
            else
            {
                calculate(Double.parseDouble(display.getText()));
                lastCommand=command;
                start=true;
            }
        }
    }
    这段你当中的if(start)这里的Start是什么变量啊~！！是判断什么的啊？