calculator.java

碟片出租系统,后台是SQL SERVER,联系编程时可以全部采用或者部分采用.

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

public class Calculator extends MyDialog implements ActionListener
{
	final int INIT =0, RUN = 1, ERROR = 2, ADD = 1, SUB = 2, MUL = 3, DIV = 4;
	JTextField screen;
	JButton button[] = new JButton[20];
	JPanel panel;
	String buttonName[] = { "7", "8", "9", "/", "C", "4", "5", "6", "×", "S",
							"1", "2", "3", "－", "％", "0",  ".", "←","＋", "＝" };
	BigDecimal accumulator = new BigDecimal( 0 );//累加器
	BigDecimal number = new BigDecimal( 0 );//第二个操作数
	boolean decimal = false;//小数标记
	int state = INIT, operate = INIT;//状态标记和操作标记
	boolean countFinish = true, inputFinish = true;//计算完成标记和操作数输入完成标记
	
	public Calculator(JFrame frame)
	{
		super(frame);
		setTitle("计算器");
		Container container = getContentPane();
		screen = new JTextField();
		screen.addKeyListener(
			new KeyAdapter()
			{
				public void keyTyped( KeyEvent ke )
				{
					char ch = ke.getKeyChar();
					JButton action = null;
					switch( ch )
					{
						case '7': action = button[0];break;
						case '8': action = button[1];break;
						case '9': action = button[2];break;
						case '/': action = button[3];break;
						case '4': action = button[5];break;
						case '5': action = button[6];break;
						case '6': action = button[7];break;
						case '*': action = button[8];break;
						case '1': action = button[10];break;
						case '2': action = button[11];break;
						case '3': action = button[12];break;
						case '-': action = button[13];break;
						case '0': action = button[15];break;
						case '.': action = button[16];break;
						case '+': action = button[18];break;
						default : action = null;
					}
					if( ke.getKeyChar() == KeyEvent.VK_ENTER ) action = button[19];
					if( ke.getKeyChar() == KeyEvent.VK_BACK_SPACE ) action = button[17];
					actionManage( action, ch + "" );
				}
			}
		);
		screen.setText( "0." );
		screen.setHorizontalAlignment( JTextField.RIGHT );
		screen.setBackground( Color.white );
		screen.setEditable( false );
		container.add( screen, BorderLayout.NORTH );
		panel = new JPanel();
		panel.setLayout( new GridLayout( 4, 5, 5, 5 ) );
		for( int i = 0; i < buttonName.length; i ++ )
		{
			button[i] = new JButton( buttonName[i] );
			button[i].addActionListener( this );
			panel.add( button[i] );
		}
		container.add( panel, BorderLayout.CENTER );
		setSize( 270, 190 );
		setLocation();
	}
	
	public void actionPerformed( ActionEvent ae ) 
	{
		JButton action = ( JButton ) ae.getSource();
		actionManage( action, ae.getActionCommand() );
		screen.grabFocus();
	}
	
	private void actionManage( JButton action, String num )
	{
		if( !( state == ERROR && action != button[4] ) )
		{//当状态是ERROR时，只有C按钮有效
			stop1: for( int i = 0; i < button.length; i ++ )
			{
				if( action == button[i] )
				{
					switch( i )
					{
						case 3:///
							manageOperation();
							operate = DIV;
							break stop1;
						case 4://c
							init();
							break stop1;
						case 8://*
							manageOperation();
							operate = MUL;
							break stop1;
						case 9://s
							squareRoot();
							break stop1;
						case 13://-
							manageOperation();
							operate = SUB;
							break stop1;
						case 14://%
							pressEquals();
							if( operate == DIV )//只有除操作时％才有意义
							{
								accumulator = accumulator.movePointRight( 2 );
								setScreenText( accumulator );							
							}
							break stop1;
						case 16://.
							decimal = true;
							break stop1;
						case 17://<-只有刚输入的数据才可以退格
							//当countFinish=true时说明显示为计算结果，不能退格
							if( !countFinish ) backSpace();
							break stop1;
						case 18://+
							manageOperation();
							operate = ADD;
							break stop1;
						case 19://=
							pressEquals();
							break stop1;
						default ://数字
							pressNumber( num );
							break stop1;
					}
				}
			}
		}
	}
	public void setVisible(boolean isVisible)
	{
		super.setVisible(isVisible);
		if(isVisible) init();
	}
	
	private void init()
	{
		screen.setText( "0." );
		operate = INIT;
		state = INIT;
		decimal = false;
		accumulator = BigDecimal.valueOf( 0 );
		number = BigDecimal.valueOf( 0 );
		countFinish = true;
		inputFinish = true;
	}
	
	private void squareRoot()
	{
		String result = screen.getText();
		double num =Double.parseDouble( result );
		if( num < 0 )
		{
			state = ERROR;
			screen.setText( "负数不能开根号！" );
		}
		else
		{
		num = Math.sqrt( num );
		result = num + "";
		char ch = result.charAt( result.length() - 1 );
		while( ch == '0' )
		{
			result = result.substring( 0, result.length() - 1 );
			ch = result.charAt( result.length() - 1 );
		}
		screen.setText( result );
		}
		inputFinish = true;

	}
	
	private void pressEquals()
	{
		inputFinish = true;
		decimal = false;
		//当countFinish=false时说明计算没完成，屏幕显示为第二个操作数，要取下此操作数
		//当countFinish=true并且state=RUN时说明第一个操作数和操作输入后按等号，此时没有第二个操作数
		if( !countFinish || countFinish && state == RUN ) 
			number = new BigDecimal( screen.getText() );
		state = INIT;//按等号后一般说明计算结果，状态为初始化状态
		count( operate );
	}
	
	private void manageOperation()
	{
		inputFinish = true;
		decimal = false;
		//当countFinish=true时说明输入的是下一次计算的操作，只记下下一次计算操作，不计算
		if( !countFinish )
		{
			//当state!=INIT时说明要计算，取第二个操作数计算
			if( state != INIT ) 
			{
				number = new BigDecimal( screen.getText() );
				count( operate );
			}
			//当state=INIT时说明第一次输入操作，不用计算
			else
			{
				state = RUN;//进入计算状态
				countFinish = true;//防止初始化并输入第一个数据之后连续按两下运算时计算出结果
				accumulator = new BigDecimal( screen.getText() );
			}
		}
	}
	
	private void count( int operate )
	{
		switch( operate )
		{
			case 1://+
				accumulator = accumulator.add( number );
				break;
			case 2://-
				accumulator = accumulator.subtract( number );
				break;
			case 3://*
				accumulator = accumulator.multiply( number );
				break;
			case 4:///
				try
				{
					accumulator = accumulator.divide( number, 15, 5 );
				}catch(  ArithmeticException ae )
				{
					state = ERROR;
				}
				
				break;
		}
		setScreenText( accumulator );
		if( state == ERROR ) screen.setText( "除数不能为零！" );
		countFinish = true;
	}
	
	private void setScreenText( BigDecimal number )//去掉小数中最右边的0后显示
	{
		String result = number.toString();
		if( result.indexOf( "." ) != -1 )
		{
			char ch = result.charAt( result.length() - 1 );
			while( ch == '0' )
			{
				result = result.substring( 0, result.length() - 1 );
				ch = result.charAt( result.length() - 1 );
			}
		}
		else
		{
			result += ".";
		}	
		screen.setText( result );
	}
	
	private void backSpace()
	{
		try
		{
			//只输入一位的整数的长度是2，小数是3，退格后清0
			if( screen.getText().length() == 2 || 
					screen.getText().length() == 3 && decimal == true ) 
				screen.setText( "0." );
			else if( decimal == false )
			{
				screen.setText( screen.getText( 0, screen.getText().length() - 2 ) + "." );
			}
			else if( decimal == true )
			{
				//当小数退格到最后一位是.时再按退格时小数标设为假
				if( screen.getText( screen.getText().length() - 1, 1 ).equals( "." ) )
					decimal = false;
				else
					screen.setText( screen.getText( 0, screen.getText().length() - 1 ) );
			}
		}catch( Exception e ){				}
	}
	
	private void pressNumber( String num )
	{
		//当inputFinish=true时说明上一步按了操作，现在要输入第二个操作数，屏幕清0
		if( inputFinish )
		{
			screen.setText( "0." );
			inputFinish = false;
		}
		countFinish = false;//当输入操作数时说明有新的计算，计算完成标记设为假
		//输入第一位整数的处理
		if( screen.getText().equals( "0." ) && decimal == false ) screen.setText( num + "." );
		else
		{
			if( decimal == false )//输入为整数的处理
			{				
				try
				{
					screen.setText( screen.getText( 0, screen.getText().length() - 1 )
									+ num + "." );
				}catch( Exception e ){				}
			}
			else//输入为小数的处理
			{
				screen.setText( screen.getText() + num );
			}
		}
	}
}