以前用java写的计算器程序

import Java.awt.*;

import java.awt.event.*;

import javax.Swing.*;

public class Calculator extends JFrame

{

private Container container;

private GridBagLayout layout;

private GridBagConstraints constraints;

private JTextField displayField;//计算结果显示区

private String lastCommand;//保存 ,-,*,/,=命令

private double result;//保存计算结果

private boolean start;//判断是否为数字的开始

public Calculator()

{

super("Calculator");

container=getContentPane();

layout=new GridBagLayout();

container.setLayout(layout);

constraints=new GridBagConstraints();

start=true;

result=0;

lastCommand = "=";

displayField=new JTextField(20);

displayField.setHorizontalAlignment(JTextField.RIGHT);

constraints.gridx=0;

constraints.gridy=0;

constraints.gridwidth=4;

constraints.gridheight=1;

constraints.fill=GridBagConstraints.BOTH;

constraints.weightx=100;

constraints.weighty=100;

layout.setConstraints(displayField,constraints);

container.add(displayField);

ActionListener insert = new InsertAction();

ActionListener command = new CommandAction();

addButton("Backspace",0,1,2,1,insert);

addButton("CE",2,1,1,1,insert);

addButton("C",3,1,1,1,insert);

addButton("7",0,2,1,1,insert);

addButton("8",1,2,1,1,insert);

addButton("9",2,2,1,1,insert);

addButton("/",3,2,1,1,command);

addButton("4",0,3,1,1,insert);

addButton("5",1,3,1,1,insert);

addButton("6",2,3,1,1,insert);

addButton("*",3,3,1,1,command);

addButton("1",0,4,1,1,insert);

addButton("2",1,4,1,1,insert);

addButton("3",2,4,1,1,insert);

addButton("-",3,4,1,1,command);

addButton("0",0,5,1,1,insert);

addButton(" /-",1,5,1,1,insert);//只显示"-"号," "没有实用价值

addButton(".",2,5,1,1,insert);

addButton(" ",3,5,1,1,command);

addButton("=",0,6,4,1,command);

setSize(300,300);

setVisible(true);

}

private void addButton(String label,int row,int column,int with,int height,ActionListener listener)

{

JButton button=new JButton(label);

constraints.gridx=row;

constraints.gridy=column;

constraints.gridwidth=with;

constraints.gridheight=height;

constraints.fill=GridBagConstraints.BOTH;

button.addActionListener(listener);

layout.setConstraints(button,constraints);

container.add(button);

}

private class InsertAction implements ActionListener

{

public void actionPerformed(ActionEvent event)

{

String input=event.getActionCommand();

if (start)

{

displayField.setText("");

start=false;

if(input.equals(" /-"))

displayField.setText(displayField.getText() "-");

}

if(!input.equals(" /-"))

{

if(input.equals("Backspace"))

{

String str=displayField.getText();

if(str.length()>0)

displayField.setText(str.substring(0,str.length()-1));

}

else if(input.equals("CE")||input.equals("C"))

{

displayField.setText("0");

start=true;

}

else

displayField.setText(displayField.getText() input);

}

}

}

private class CommandAction implements ActionListener

{

public void actionPerformed(ActionEvent evt)

{

String command=evt.getActionCommand();

if(start)

{

lastCommand=command;

}

else

{

calculate(Double.parseDouble(displayField.getText()));

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