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);

  }

}