4.java

里面有我的JAVA实验和一些教程

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.show();
 }
}
/* *
带有计算器面板的JFrame窗口
*/
class CalculatorFrame extends JFrame
{
 public CalculatorFrame()
 {
  setTitle("Calculator");
  Container contentPane=getContentPane();
  CalculatorPanel panel=new CalculatorPanel();
  contentPane.add(panel);
  setSize(300,300);
 }
}
/* *
带有计算器按钮和一个输出显示栏的JPanel面板
*/
class CalculatorPanel extends JPanel
{
private JLabel display;
private JPanel panel;
private double result;
private String lastCommand;
private boolean start;
public CalculatorPanel()
{
 setLayout(new BorderLayout());
 result=0;
 lastCommand="=";
 start=true;
 //添加显示标签栏
 display=new JLabel("0");
 add(display,BorderLayout.NORTH);
 ActionListener insert=new InsertAction();
 ActionListener command=new CommandAction();
 //在4x4网格中添加数字和运算符按钮
 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
{
 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
{
 public void actionPerformed(ActionEvent evt)
 {
  String command=evt.getActionCommand();
  if(start)
  {
   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);
}
}