用JAVA实现一个计算器的应用程序

最新问答

• mrs探险家

  /**
  @version 1.32 2004-05-05
  @author Cay Horstmann
  */
  
  import java.awt.*;
  import java.awt.event.*;
  import javax.swing.*;
  
  public class Calculator
  {
  public static void main(String[] args)
  {
  CalculatorFrame frame = new CalculatorFrame();
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  frame.setVisible(true);
  }
  }
  
  /**
  A frame with a calculator panel.
  */
  class CalculatorFrame extends JFrame
  {
  public CalculatorFrame()
  {
  setTitle("Calculator");
  CalculatorPanel panel = new CalculatorPanel();
  add(panel);
  pack();
  }
  }
  
  /**
  A panel with calculator buttons and a result display.
  */
  class CalculatorPanel extends JPanel
  {
  public CalculatorPanel()
  {
  setLayout(new BorderLayout());
  
  result = 0;
  lastCommand = "=";
  start = true;
  
  // add the display
  
  display = new JButton("0");
  display.setEnabled(false);
  add(display, BorderLayout.NORTH);
  
  ActionListener insert = new InsertAction();
  ActionListener command = new CommandAction();
  
  // add the buttons in a 4 x 4 grid
  
  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);
  }
  
  /**
  Adds a button to the center panel.
  @param label the button label
  @param listener the button listener
  */
  private void addButton(String label, ActionListener listener)
  {
  JButton button = new JButton(label);
  button.addActionListener(listener);
  panel.add(button);
  }
  
  /**
  This action inserts the button action string to the
  end of the display text.
  */
  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);
  }
  }
  
  /**
  This action executes the command that the button
  action string denotes.
  */
  private class CommandAction implements ActionListener
  {
  public void actionPerformed(ActionEvent event)
  {
  String command = event.getActionCommand();
  
  if (start)
  {
  if (command.equals("-"))
  {
  display.setText(command);
  start = false;
  }
  else
  lastCommand = command;
  }
  else
  {
  calculate(Double.parseDouble(display.getText()));
  lastCommand = command;
  start = true;
  }
  }
  }
  
  /**
  Carries out the pending calculation.
  @param x the value to be accumulated with the prior result.
  */
  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 JButton display;
  private JPanel panel;
  private double result;
  private String lastCommand;
  private boolean start;
  }
  
  为java核心技术的计算器实现的程序，o(∩_∩)o...哈哈

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