java实现简单计算器功能

童鞋们，是不是有使用计算器的时候，还要进入运行，输入calc，太麻烦了，有时候甚至还忘记单词怎么拼写，呵呵
程序员自己写代码实现，又简单，又方便啊

以下为代码（想要生成可执行工具可参考：http://www.cnblogs.com/holdon521/p/4483966.html）

package com;
 
import java.awt.BorderLayout;
 
import java.awt.EventQueue;
 
import java.awt.Font;
 
import java.awt.GridLayout;
 
import java.awt.event.ActionEvent;
 
import java.awt.event.ActionListener;
 
import javax.swing.JButton;
 
import javax.swing.JFrame;
 
import javax.swing.JPanel;
 
import javax.swing.JTextField;
 
import javax.swing.SwingConstants;
 
import javax.swing.UIManager;
 
import javax.swing.border.EmptyBorder;
 
public class Test  extends JFrame{
 
/**
 
   *  humphrey
 
   */
 
  private static final long serialVersionUID = -9075562467166618473L;
 
  private JPanel contentPane;
 
  private JTextField display;
 
  private ActionListener insert = new InsertAction();
 
  private ActionListener command = new CommandAction();
 
  private double result = 0;
 
  private String lastCommand = "=";
 
  private boolean start = true;
 
  /**
 
   * Launch the application.
 
   */
 
  public static void main(String[] args) {
 
      try {
 
          UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
 
      } catch (Throwable e) {
 
          e.printStackTrace();
 
      }
 
      EventQueue.invokeLater(new Runnable() {
 
          public void run() {
 
              try {
 
                  Test frame = new Test();
 
                  frame.setVisible(true);
 
              } catch (Exception e) {
 
                  e.printStackTrace();
 
              }
 
          }
 
      });
 
  }
 
  /**
 
   * Create the frame.
 
   */
 
  public Test() {
 
      setTitle("\u8BA1\u7B97\u5668");
 
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
      setLocationByPlatform(true);
 
      contentPane = new JPanel();
 
      contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
 
      contentPane.setLayout(new BorderLayout(0, 0));
 
      setContentPane(contentPane);
 
      JPanel displayPanel = new JPanel();
 
      contentPane.add(displayPanel, BorderLayout.NORTH);
 
      display = new JTextField();
 
      display.setText("0");
 
      display.setHorizontalAlignment(SwingConstants.RIGHT);
 
      display.setEditable(false);
 
      display.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      displayPanel.add(display);
 
      display.setColumns(13);
 
      JPanel buttonPanel = new JPanel();
 
      contentPane.add(buttonPanel, BorderLayout.CENTER);
 
      buttonPanel.setLayout(new GridLayout(4, 4, 5, 5));
 
      JButton number7Button = new JButton("7");
 
      number7Button.addActionListener(insert);
 
      number7Button.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(number7Button);
 
      JButton number8Button = new JButton("8");
 
      number8Button.addActionListener(insert);
 
      number8Button.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(number8Button);
 
      JButton number9Button = new JButton("9");
 
      number9Button.addActionListener(insert);
 
      number9Button.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(number9Button);
 
      JButton divideButton = new JButton("/");
 
      divideButton.addActionListener(command);
 
      divideButton.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(divideButton);
 
      JButton number4Button = new JButton("4");
 
      number4Button.addActionListener(insert);
 
      number4Button.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(number4Button);
 
      JButton number5Button = new JButton("5");
 
      number5Button.addActionListener(insert);
 
      number5Button.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(number5Button);
 
      JButton number6Button = new JButton("6");
 
      number6Button.addActionListener(insert);
 
      number6Button.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(number6Button);
 
      JButton multiplyButton = new JButton("*");
 
      multiplyButton.addActionListener(command);
 
      multiplyButton.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(multiplyButton);
 
      JButton number3Button = new JButton("1");
 
      number3Button.addActionListener(insert);
 
      number3Button.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(number3Button);
 
      JButton number2Button = new JButton("2");
 
      number2Button.addActionListener(insert);
 
      number2Button.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(number2Button);
 
      JButton number1Button = new JButton("3");
 
      number1Button.addActionListener(insert);
 
      number1Button.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(number1Button);
 
      JButton subtractButton = new JButton("-");
 
      subtractButton.addActionListener(command);
 
      subtractButton.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(subtractButton);
 
      JButton number0Button = new JButton("0");
 
      number0Button.addActionListener(insert);
 
      number0Button.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(number0Button);
 
      JButton dotButton = new JButton(".");
 
      dotButton.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(dotButton);
 
      JButton equalButton = new JButton("=");
 
      equalButton.addActionListener(command);
 
      equalButton.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(equalButton);
 
      JButton addButton = new JButton("+");
 
      addButton.addActionListener(command);
 
      addButton.setFont(new Font("微软雅黑", Font.PLAIN, 15));
 
      buttonPanel.add(addButton);
 
      pack();
 
  }
 
  private class InsertAction implements ActionListener {
 
      public void actionPerformed(ActionEvent e) {
 
          String input = e.getActionCommand();
 
          String text = display.getText();
 
          if (start) {
 
              display.setText("");
 
              start = false;
 
          }
 
          if (text.startsWith(".")) {
 
              display.setText("0" + display.getText() + input);
 
          } else if (text.startsWith("-0.") || text.startsWith("0.")) {
 
              display.setText(display.getText() + input);
 
          } else if (text.startsWith("-0")) {
 
              display.setText("-" + input);
 
          } else if (text.startsWith("0")) {
 
              display.setText(input);
 
          } else {
 
              display.setText(display.getText() + input);
 
          }
 
      }
 
  }
 
  private class CommandAction implements ActionListener {
 
      public void actionPerformed(ActionEvent e) {
 
          String command = e.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) {
 
      char operator = lastCommand.charAt(0);
 
      switch (operator) {
 
          case '+':
 
              result += x;
 
              break;
 
          case '-':
 
              result -= x;
 
              break;
 
          case '*':
 
              result *= x;
 
              break;
 
          case '/':
 
              result /= x;
 
              break;
 
          case '=':
 
              result = x;
 
              break;
 
      }
 
      display.setText("" + result);
 
  }
 
}