java计算器的是实现

package calculator;

import java.awt.EventQueue;

public class Calculator {

 

  public static void main(String[] args) {

    EventQueue.invokeLater(new Runnable(){

      @Override

      public void run() {

        CalculatorFrame frame = new CalculatorFrame();

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.setVisible(true);

      }

     

    });

  }

}

 

 

package calculator;

import javax.swing.JFrame;

public class CalculatorFrame extends JFrame {

 

  public CalculatorFrame(){

    setTitle("Calculator");

    CalculatorPanel panel = new CalculatorPanel();

    add(panel);

    pack();

  }

}

package calculator;

import java.awt.BorderLayout;

public class CalculatorPanel extends JPanel{

 

  /**

   *

   */

  private static final long serialVersionUID = 1L;

  private JButton display;

  private JPanel panel;

  private double result;

  private String lastCommand;

  private boolean start;

 

  public CalculatorPanel(){

    setLayout(new BorderLayout());

    result = 0;

    lastCommand = "";

    start = true;

   

    display = new JButton("0");

    display.setEnabled(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{

    @Override

    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{

    @Override

    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;

      }

    }

    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);

    }

  }

 

}