用java实现简单的计算器

package GUI;import javax.swing.*;import java.util.*;import java.awt.*;import java.awt.event.*;/** * * @author Zhu Zhengyan */public class My_GUI3 {    public static void main(String[] args)    {        EventQueue.invokeLater(()->        {            JFrame frame = new CalculatorFrame();            frame.setTitle("Calculator");            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);            frame.setVisible(true);        });    }    }class CalculatorFrame extends JFrame    {        public CalculatorFrame()        {            JPanel panel  = new CalculatorPanel();            add(panel);            pack();        }    }

计算器panel
core java 1第10版  p479,感觉书上不好，下面是我改进后的代码

事件处理、布局、组件

package GUI;import java.awt.*;import java.awt.event.*;import javax.swing.*;/** * * @author Zhu Zhengyan */public class CalculatorPanel extends JPanel{    private JButton display;    private double result;    private String lastCommand;    private boolean start;    private JPanel panel_1 = new JPanel();    private JPanel panel_2 = new JPanel();        public CalculatorPanel()    {        setLayout(null);        setSize(600,500);                result = 0;        lastCommand = "+";        start = true;                display = new JButton("0");        display.setEnabled(false);        display.setBounds(0,0,600,100);                ActionListener insert = new InsertAction();        ActionListener command = new CommandAction();                panel_1.setLayout(null);        panel_1.setBounds(0,0,600,100);        panel_2.setLayout(new GridLayout(4,4));        panel_2.setBounds(0,100,600,400);        display.setFont(new Font("宋体",Font.PLAIN,32));        display.setForeground(Color.RED);   //设置button中text的颜色···因为Enabled是false，所以不会变        panel_1.add(display);        add(panel_1);                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_2);            }    private void addButton(String label,ActionListener listener)//定义一个一步添加button和listener的方法    {        JButton button = new JButton(label);        button.addActionListener(listener);        button.setFont(new Font("宋体",Font.PLAIN,28));   //设置button中text || 3个参数是：字体、样式(粗体斜体等)、大小(字号)        button.setForeground(new Color(139,69,19));       //自己调色用new Color        panel_2.add(button);       //注意此处是panel_2    }    private class InsertAction  implements ActionListener    {        public void actionPerformed(ActionEvent event)    //重写动作执行方法        {                                                 //这个方法是，每按一个数字按钮，屏幕上就显示这个按钮的            String input = event.getActionCommand();      //text，并拼接在一起（计算器的输入一个数）            if(start)                                                  {                display.setText("");                start = false;            }            display.setText(display.getText()+input);//这个计算器，表面显示0，实际上是0+                                                                     }    }      private class CommandAction implements ActionListener           {            public void actionPerformed(ActionEvent event)    //每输入一个符号，就进行一次运算，不显示            {                String command = event.getActionCommand();                if(command.equals("="))                                        {                    calculate(Double.parseDouble(display.getText()));                    display.setText(String.valueOf(result));    //当用户输入=，就把运算结果显示出来                    result = 0;                      //这三步是重置计算器                    lastCommand = "+";                    start = true;                }                else                {                    calculate(Double.parseDouble(display.getText()));                    display.setText(command);       //显示用户按下的运算符号                    lastCommand = command;                    start = true;                   //start = true时，就可以输入另外的数了                }            }        }            public void calculate(double x)       //计算器的计算方法    {        if(lastCommand.equals("+"))            result += x;        else if(lastCommand.equals("-"))            result -= x;        else if(lastCommand.equals("*"))            result *= x;        else if(lastCommand.equals("/"))            result /= x;    }    public Dimension getPreferredSize()    {        return new Dimension(600,500);    }}