java Swing 的一个简单的计算器

//实现了 =、-、+、*、/等基本的操作

 

package Calculator;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Calculate extends JFrame {

	public static final int WIDTH = 500 ;
	public static final int HEIGHT = 400 ;
	
	private JTextField result; 
	
	private JPanel mainPane; //主面板 
	private JPanel numPane; //数字面板 
	private JPanel operatePane; //操作符面板 
	private JPanel showPane; //显示面板 
	
	private JButton[] numB; //数字按钮 
	private JButton[] operateB; //操作符面板 
	
	public Calculate(String title){
		
		setTitle(title) ;
		
		result = new JTextField("0.0",22) ;
		result.setEditable(false) ;
		
		mainPane = new JPanel() ;
		numPane = new JPanel() ;
		operatePane = new JPanel() ;
		showPane = new JPanel() ;
		
		numB = new JButton[12] ;
		for(int i=0; i<9; i++) 
		{ 
			numB[i] = new JButton(new Integer(i+1).toString()); 
		} 
		numB[9] = new JButton("0"); 
		numB[10] = new JButton("cls"); 
		numB[11] = new JButton("."); 
		//将数字按钮加到数字面板上
		numPane.setLayout(new GridLayout(4,3,1,1)) ;
		for(int i=0;i<12;i++)
			numPane.add(numB[i]) ;
		
		operateB = new JButton[8] ;
		operateB[0] = new JButton("+"); 
		operateB[1] = new JButton("-"); 
		operateB[2] = new JButton("*"); 
		operateB[3] = new JButton("/"); 
		operateB[4] = new JButton("pow"); 
		operateB[5] = new JButton("sqrt"); 
		operateB[6] = new JButton("+/-"); 
		operateB[7] = new JButton("=");
		//把操作符按钮添加到操作面板上
		operatePane.setLayout(new GridLayout(4,2,1,1)) ;
		for(int i=0; i<8; i++) 
			operatePane.add(operateB[i]) ;
		
		showPane.setLayout(new BorderLayout()) ;
		showPane.add(result, BorderLayout.NORTH); 
		
		mainPane.setLayout(new BorderLayout()) ;
		mainPane.add(showPane, BorderLayout.NORTH); 
		mainPane.add(numPane, BorderLayout.WEST); 
		mainPane.add(operatePane, BorderLayout.EAST); 
		
		this.add(mainPane, BorderLayout.CENTER); 
		this.setSize(WIDTH, HEIGHT); 
		
		/*try{
			//将LookAndFeel设置成windows样式
			UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel") ;
		}catch(Exception e){
			e.printStackTrace() ;
		}*/
		
		Toolkit too = Toolkit.getDefaultToolkit() ;
		Dimension screenSize = too.getScreenSize() ;
		this.setLocation((screenSize.width-WIDTH)/2, (screenSize.height-HEIGHT)/2) ;
		
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ;
		this.setResizable(false); 
		this.pack(); 
		
		ButtonListener button = new ButtonListener() ;
		for(int i = 0; i < numB.length; i++)
			numB[i].addActionListener(button) ;
		for(int i=0;i<operateB.length;i++)
			operateB[i].addActionListener(button) ;
		
	}

	class ButtonListener implements ActionListener 
	{ 
		private String last; //存储上一此操作符 
		private String strVal; //存储数字对应的字符串 
		private double total; //总数 
		private double number; //存储新输入的数 
		private boolean firsttime; //判断是否第一次按下的是操作符按钮 
		private boolean operatorPressed;//判断是否已经按过操作符按钮 

		public ButtonListener() 
		{ 
			firsttime = true; 
			strVal = ""; 
		}
	
		//事件处理
		public void actionPerformed(ActionEvent e){
		
			String str = ((JButton)e.getSource()).getText().trim() ;
			if(Character.isDigit(str.charAt(0)))
				handleNumber(str) ;
			else
				calculate(str) ;
		
		}
	
		//判断是一元操作符还是二元操作符，并根据操作符类型做计算 
		public void calculate(String op) 
		{ 
			operatorPressed = true; 
			
			if(firsttime && !isUnary(op)) 
			{ 
				total = getNumberOnDisplay(); 
				firsttime = false; 
			} 
			if(isUnary(op)) 
			{ 
				handleUnaryOp(op); 
			} 
			else if(last != null) 
			{ 
				handleBinaryOp(last); 
			} 
			if(! isUnary(op)) 
			{ 
				last = op; 
			} 
		} 
	
		//判断是否一元操作符 
		public boolean isUnary(String s) 
		{ 
			return s.equals("=") || s.equals("cls") || s.equals("sqrt") 
									|| s.equals("+/-") || s.equals("."); 
		} 

		//处理一元操作符 
		public void handleUnaryOp(String op) 
		{ 
			if(op.equals("+/-")) 
			{
				number = negate(getNumberOnDisplay() + ""); 
				result.setText(""); 
				result.setText(number + ""); 
				return; 
			}
			else if(op.equals(".")) 
			{ 
				handleDecPoint(); 
				return; 
			}
			else if(op.equals("sqrt")) 
			{ 
				number = Math.sqrt(getNumberOnDisplay()); 
				result.setText(""); 
				result.setText(number + ""); 
				return; 
			}
			else if(op.equals("=")) 
			{// 
				if(last!= null && !isUnary(last)) 
				{ 
					handleBinaryOp(last); 
				} 
				last = null; 
				firsttime = true; 
				return; 
			}
			else 
			{ 
				clear(); 
			} 
		} 

		//处理二元运算符 
		public void handleBinaryOp(String op) 
		{ 
			if(op.equals("+")) 
			{ 
				total +=number; 
			}
			else if(op.equals("-")) 
			{ 
				total -=number; 
			}
			else if(op.equals("*")) 
			{ 
				total *=number; 
			}
			else if(op.equals("/")) 
			{ 
				try 
				{ 
					total /=number; 
				}catch(ArithmeticException ae){} 
			}
			else if(op.equals("pow")) 
				total = Math.pow(total, number); 
			//result.setText(""); 
			last = null; 
			// strVal = ""; 
			number = 0; 
			result.setText(total + ""); 
		} 

		//该方法用于处理数字按钮 
		public void handleNumber(String s) 
		{ 
			if(!operatorPressed) 
			{ 
				strVal += s; 
			}
			else 
			{ 
				operatorPressed = false; 
				strVal = s; 
			} 
		 
			number = new Double(strVal).doubleValue(); 
			result.setText(""); 
			result.setText(strVal); 
		} 

		//该方法用于按下"."按钮 
		public void handleDecPoint() 
		{ 
			operatorPressed = false; 
	 
			if(strVal.indexOf(".")<0) 
			{ 
				strVal += "."; 
			} 
			result.setText(""); 
			result.setText(strVal); 
		} 

		//该方法用于将一个数求反 
		public double negate(String s) 
		{ 
			operatorPressed = false; 
			//如果是一个整数，去掉小数点后面的0 
			if(number == (int)number) 
			{ 
				s = s.substring(0,s.indexOf(".")); 
			} 

			//如果无"-"增加在该数的前面 
			if(s.indexOf("-")<0) 
			{ 
				strVal = "-" + s; 
			} 
			else 
			{ 
				strVal = s.substring(1); 
			} 
			return new Double(strVal).doubleValue(); 
		} 

		//将显示框中的值转换成Double 
		public double getNumberOnDisplay() 
		{ 
			return new Double(result.getText()).doubleValue(); 
		} 

		//清除屏幕并设置所有的标识 
		public void clear() 
		{ 
			firsttime = true; 
			last = null; 
			strVal = ""; 
			total = 0; 
			number = 0; 
			result.setText("0"); 
		} 
	}

	public static void main(String[] args) { 
		Calculate c = new Calculate("简单的计算器程序"); 
		c.setVisible(true); 
	} 
}