java简单的计算器类

package chap;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Calculator {
	private JFrame frame;
	private JPanel panel,panelKeys,panelKeys_up,panelKeys_down;
	
	private JTextField textComputer;//计算区域
	private JButton buttonBk,buttonC;//退格键和清零键
	private JButton button[];//数字键组
	private JButton buttonDot,buttonAddSub,buttonAdd,buttonSub,buttonMul,buttonDiv,button1,button2,button3,buttonEqual;
	
	private double result;//计算结果
	private final short ADD = 1;
	private final short SUB = 2;
	private final short MUL = 3;
	private final short DIV = 4;
	private short operator = -1;//运算符
	
	public Calculator(){
		frame = new JFrame("计算机");
		frame.setSize(400, 250);
		panel = new JPanel();//全局面板
		panel.setVisible(true);
		frame.setVisible(true);
		frame.getContentPane().add(panel);
		ActionListener listener = new ComputerActionListener();//按键监听器

		//计算区
		textComputer = new JTextField(15);
		textComputer.setText("");
		textComputer.setEditable(false);
		textComputer.setBackground(new Color(255,255,255));
		//功能键上半部分
		panelKeys_up = new JPanel();
		panelKeys_up.setLayout(new FlowLayout(FlowLayout.RIGHT));
		
		buttonBk = new JButton("Backspace");
		buttonBk.setForeground(new Color(255,0,0));
		
		buttonC = new JButton("C");
		buttonC.setForeground(new Color(255,0,0));
		
		buttonBk.addActionListener(listener);
		buttonC.addActionListener(listener);
		
		panelKeys_up.add(buttonBk);
		panelKeys_up.add(buttonC);

		//功能键下半部分
		panelKeys_down = new JPanel();
		panelKeys_down.setLayout(new GridLayout(4,5));
		button = new JButton[10];
		for(int i = 0;i < button.length;i++){
			button[i] = new JButton(Integer.toString(i));
			button[i].setForeground(new Color(255,0,0));
		}
		
		buttonAddSub = new JButton("+/-");
		buttonAddSub.setForeground(new Color(255,0,0));
		buttonAdd = new JButton("+");
		buttonAdd.setForeground(new Color(255,0,0));
		buttonSub = new JButton("-");
		buttonSub.setForeground(new Color(255,0,0));
		buttonMul = new JButton("*");
		buttonMul.setForeground(new Color(255,0,0));
		buttonDiv = new JButton("/");
		buttonDiv.setForeground(new Color(255,0,0));
		button1 = new JButton();
		button2 = new JButton();
		button3 = new JButton();
		button1.setForeground(new Color(255,0,0));
		button2.setForeground(new Color(255,0,0));
		button3.setForeground(new Color(255,0,0));
		buttonEqual = new JButton("=");
		buttonEqual.setForeground(new Color(255,0,0));
		
		buttonAddSub.addActionListener(listener);
		buttonAdd.addActionListener(listener);
		buttonSub.addActionListener(listener);
		buttonMul.addActionListener(listener);
		buttonDiv.addActionListener(listener);
		buttonEqual.addActionListener(listener);
		for(int i = 0 ; i <=9 ; i++){
			button[i].addActionListener(listener);
		}
		
		for(int i = 0 ; i <=9 ; i++){
			panelKeys_down.add(button[i]);
		}
		panelKeys_down.add(buttonAddSub);
		panelKeys_down.add(buttonAdd);
		panelKeys_down.add(buttonSub);
		panelKeys_down.add(buttonMul);
		panelKeys_down.add(buttonDiv);
		panelKeys_down.add(buttonEqual);
		
		panel.setLayout(new BorderLayout());
		panel.add(textComputer,BorderLayout.NORTH);
		panel.add(panelKeys_up,BorderLayout.CENTER);
		panel.add(panelKeys_down,BorderLayout.SOUTH);
	}
	class ComputerActionListener implements ActionListener{

		@Override
		public void actionPerformed(ActionEvent event) {
			// TODO Auto-generated method stub
			Object keyButton = event.getSource();
			String text = textComputer.getText();
			DecimalFormat df = new DecimalFormat("0.###########");
			
			//Backspace
			if(keyButton == buttonBk && text.length() > 0){
				textComputer.setText(text.substring(0,text.length()-1));
			}
			
			//C键
			if(keyButton == buttonC){
				result = 0;
				textComputer.setText("");
			}
			
			//数字键
			for(int i=0;i<10;i++){
				if(keyButton == button[i]){
					textComputer.setText(text+i);
				}
			}
			
			if(keyButton == buttonAdd){
				operator = 1;
			}
			if(keyButton == buttonSub){
				operator = 2;
			}
			if(keyButton == buttonMul){
				operator = 3;
			}
			if(keyButton == buttonDiv){
				operator = 4;
			}
			
			//符号键
			if(keyButton == buttonAdd || keyButton == buttonSub || keyButton == buttonMul || keyButton == buttonDiv || keyButton == buttonEqual){
				switch(operator){
				case ADD:
					result += Double.parseDouble(text);
					break;
				case SUB:
					result -=Double.parseDouble(text);
					break;
				case MUL:
					result *=Double.parseDouble(text);
					break;
				case DIV:
					result /=Double.parseDouble(text);
					break;
				default:
					result = Double.parseDouble(text);
				}
				textComputer.setText("");
			}
			
			if(keyButton == buttonEqual){
				textComputer.setText(String.valueOf(result));
			}
		}
		
	}
	public static void main(String args[]){
		new Calculator();
	}
}