listener.java

Java 开发实例:利用java做一个简单的计算器 两个类。还只是完成+、-、×、÷运算而已

package calc_ls;

import java.awt.Button;
import java.awt.Checkbox;
import java.awt.event.*;

public class Listener extends WindowAdapter implements ActionListener,WindowListener,ItemListener
{
	static StringBuffer buffer = new StringBuffer("0");
	float a = 0,b = 0;
	boolean aIsEmpty = true;
	boolean bIsEmpty = true;
	char theta = '+';
	public boolean isOP(char character)                 //判断字符是否为运算符
	{
		if (character == '+')
			return true;
		else if (character == '-')
			return true;
		else if (character == '*')
			return true;
		else if (character == '/')
			return true;
		else if (character == '(')
			return true;
		else if (character == ')')
			return true;
		else if (character == '#')
			return true;
		return false;
	}//isOP
	
	public StringBuffer getTempBuffer(StringBuffer exp)      //从exp中获得一个运算数或运算符
	{
		int bufferCount = -1;  
		StringBuffer buffer = new StringBuffer();
		while (exp.charAt(++bufferCount) != '|');
		buffer.append(exp.subSequence(0, bufferCount));  //取得第一个运算数
		exp.delete(0, bufferCount + 1);       //删除第一个运算数
		return buffer;
	}//getTempBuffer
	
	public int converOP(char op)            //将运算符转换为int
	{
		if (op == '+')
			return 0;
		else if (op == '-')
			return 1;
		else if (op == '*')
			return 2;
		else if (op == '/')
			return 3;
		else if (op == '(')
			return 4;
		else if (op == ')')
			return 5;
		else if (op == '#')
			return 6;
		return 0;
	}//converOP
	
	public int precede(char op1, char op2)   //确定运算符的优先权
	{
		int operatePRI[][] = {{1,1,-1,-1,-1,1,1},
				       {1,1,-1,-1,-1,1,1},
				       {1,1,1,1,-1,1,1},
				       {1,1,1,1,-1,1,1},
				       {-1,-1,-1,-1,-1,0,0},
				       {1,1,1,1,0,1,1},
				       {-1,-1,-1,-1,-1,0,0}};
		int operation1 = converOP(op1);
		int operation2 = converOP(op2);
		return operatePRI[operation1][operation2];
	}//precede
	
	public float operate(float a, char theta, float b)   //计算a theta b,其中theta为运算符, a,b为运算数
	{
		if (theta == '+')
			return a + b;
		else if (theta == '-')
			return a - b;
		else if (theta == '*')
			return a * b;
		else if (theta == '/')
			return a / b;
		else return 1;
	}//operate
	
	public float evaluateExpression(StringBuffer exp)      //计算表达式方法
	{
		StringBuffer opStack = new StringBuffer(); //运算符栈
		float numStack[] = new float[50];       //数字栈
		int numCount = -1;
		StringBuffer tempBuffer = new StringBuffer(); //定义存放取得的运算符或运算数的缓冲区
		tempBuffer = getTempBuffer(exp);
		opStack.append('#');  //向运算符栈压入标志符'#'
		//取得得字符与运算符栈顶字符不为# 循环
		while ( tempBuffer.charAt(0) != '#' || opStack.charAt(opStack.length()-1) != '#')
		{
			System.out.println("exp  "+exp);
			System.out.println(tempBuffer.length()+"  length  "+tempBuffer);
			System.out.println(opStack.charAt(opStack.length()-1));
			if ( !isOP(tempBuffer.charAt(tempBuffer.length()-1)) )
			{
				numStack[++numCount] = Float.parseFloat(tempBuffer.toString());  //将运算数入栈，运算数栈计数器加1
				tempBuffer.delete(0, tempBuffer.length());  //清空缓冲区
				tempBuffer = getTempBuffer(exp);
			}			
			else
				 switch (precede(opStack.charAt(opStack.length()-1),tempBuffer.charAt(0)))
				 {
				 case -1:       //栈顶元素优先权低
					 opStack.append(tempBuffer.charAt(0));
					 tempBuffer = getTempBuffer(exp);
					 break;
				 case 0:        //脱括号并接受下一个运算数或运算符
					 opStack.deleteCharAt(opStack.length()-1);
					 tempBuffer = getTempBuffer(exp);
					 break;
				 case 1:        //退栈并将运算结果入栈
					 char theta = opStack.charAt(opStack.length()-1);
					 opStack.deleteCharAt(opStack.length()-1);
					 float b = numStack[numCount--];
					 float a = numStack[numCount--];
					 numStack[++numCount] = operate(a,theta,b);
					 break;
				 }//switch	
			System.out.println("numStack  "+numStack[numCount]);
		}//while
		return numStack[0];				
	}//evaluateExpression

	public void windowClosing(WindowEvent e)
	{
		System.exit(1);   
	}
	public void actionPerformed(ActionEvent e) 
	{
		// TODO Auto-generated method stub
		Button btn = (Button)e.getSource();
		String tempS = btn.getLabel();
//		buffer.append(btn.getLabel());
//		CalcWindow.lab.setText(btn.getLabel());
		switch (CalcWindow.choice)
		{
		case 1:
		{
		if (!tempS.equals("=")){
		if (tempS.equals("+/-"))
		{
			if (buffer.charAt(0) == '-')
				buffer.deleteCharAt(0);
			else 
				buffer.insert(0, '-');
		}
		else if (tempS.equals("+") || tempS.equals("-") || tempS.equals("*") || tempS.equals("/"))
		{
			if (buffer.charAt(buffer.length()-2) == '+' || buffer.charAt(buffer.length()-2) == '-' 
				|| buffer.charAt(buffer.length()-2) == '*' || buffer.charAt(buffer.length()-2) == '/')
			{
				buffer.replace(buffer.length()-1, buffer.length()-1, tempS);
			}
			else if (buffer.charAt(buffer.length()-2) == '(' || buffer.charAt(buffer.length()-2) == ')')
			{
				buffer.append(tempS + "|");
			}
			else 
				buffer.append("|" + tempS + "|");
//			CalcWindow.textBuffer.append(buffer);
//			buffer = new StringBuffer();
		}
		else if (tempS.equals("."))
		{
			if (buffer.charAt(buffer.length()-1) == '.');
			else 
				buffer.append('.');			
		}
		else if (tempS.equals("<--"))
		{
			if ( buffer.length() == 1 )
				buffer.setCharAt(0, '0');				
			else
				buffer.deleteCharAt(buffer.length()-1);			
		}
		else if (tempS.equals("C"))
		{
			buffer = new StringBuffer("0");
			CalcWindow.lab.setText("0.");
		}
		else if (tempS.equals("CE"))
		{
			buffer = new StringBuffer("0");
			CalcWindow.textBuffer = new StringBuffer();
			CalcWindow.lab.setText("0.");
		}
		else if (tempS.equals("("))
		{
			if (buffer.charAt(buffer.length()-1) == '|')
				buffer.append("(|");
			else
				buffer.append("|(|");
//			CalcWindow.textBuffer.append(buffer);
//			buffer = new StringBuffer();
		}
		else if (tempS.equals(")"))
		{
			if (buffer.charAt(buffer.length()-1) == '|')
				buffer.append(")|");
			else
				buffer.append("|)|");
//			CalcWindow.textBuffer.append(buffer);
//			buffer = new StringBuffer();
		}
		else 
			buffer.append(tempS);
//		CalcWindow.textBuffer.append(buffer);
//		buffer = new StringBuffer();	
		StringBuffer bufferDisplay = new StringBuffer(buffer.toString());
		CalcWindow.lab.setText(bufferDisplay.toString().replace('|', ' '));}
		else
			{			
			CalcWindow.textBuffer.append(buffer);
			if (CalcWindow.textBuffer.charAt(CalcWindow.textBuffer.length()-1) != '|')
				CalcWindow.textBuffer.append("|#|");
			else
				CalcWindow.textBuffer.append("#|");
			float result = evaluateExpression(CalcWindow.textBuffer);
			CalcWindow.lab.setText(String.valueOf(result));
			buffer = new StringBuffer("0");
			CalcWindow.textBuffer = new StringBuffer();
//			System.out.println(CalcWindow.textBuffer);
			}
//		StringBuffer bufferDisplay = buffer;
			break;
		}//case 1
		case 2:
		{
			if (!tempS.equals("="))
			{
				if (tempS.equals("+/-"))
				{
					if (buffer.charAt(0) == '-')
						buffer.deleteCharAt(0);
					else 
						buffer.insert(0, '-');
					CalcWindow.lab.setText(buffer.toString());
				}
				else if (tempS.equals("C"))
				{
					buffer = new StringBuffer();
					CalcWindow.lab.setText("0");
				}
				else if (tempS.equals("CE"))
				{
					buffer = new StringBuffer();
					a = 0;
					b = 0;
					aIsEmpty = true;
					bIsEmpty = true;
					CalcWindow.lab.setText("0");
				}
				else if (tempS.equals("<--"))
				{
					if ( buffer.length() == 1 )
						buffer.setCharAt(0, '0');				
					else
						buffer.deleteCharAt(buffer.length()-1);	
					CalcWindow.lab.setText(buffer.toString());
				}
				else if (tempS.equals("+") || tempS.equals("-") || tempS.equals("*") || tempS.equals("/"))
				{
					if (aIsEmpty == false && bIsEmpty == false)
					{
						theta = tempS.charAt(0);
						a = Float.parseFloat(CalcWindow.lab.getText().toString());
//						bIsEmpty = true;
					}
					else if (aIsEmpty == true)
					{
						theta = tempS.charAt(0);
						if (buffer.toString().length() > 0)
							a = Float.parseFloat(buffer.toString());
						aIsEmpty = false;
						buffer = new StringBuffer();
					}
					else 
					{
						theta = tempS.charAt(0);
						if (buffer.toString().length() > 0)
							b = Float.parseFloat(buffer.toString());
						a = operate(a, theta, b);
						CalcWindow.lab.setText(a + "");
						buffer = new StringBuffer();
						bIsEmpty = false;
					}		
				}
				else 
				{
					buffer.append(tempS);
					CalcWindow.lab.setText(buffer.toString());
					bIsEmpty = true;
				}
			}
			else  //是等号 
			{				
				if (buffer.toString().length() > 0)
					b = Float.parseFloat(buffer.toString());
				a = operate(a, theta, b);
				CalcWindow.lab.setText(a + "");
				buffer = new StringBuffer();
//				a = 0;
				aIsEmpty = true;
			}			
			//...即时计算代码
		}
	}//switch
		
	}

	public void itemStateChanged(ItemEvent l) 
	{
		Checkbox chb = (Checkbox)l.getSource();
		if (chb.getLabel().equals("表达式"))
		{
			CalcWindow.choice = 1;
			CalcWindow.button_leftparenthesis.setEnabled(true);
			CalcWindow.button_rightparenthesis.setEnabled(true);
			buffer = new StringBuffer("0");
			CalcWindow.textBuffer = new StringBuffer();
			CalcWindow.lab.setText("0");
		}
		else
		{
			CalcWindow.choice = 2;
			CalcWindow.button_leftparenthesis.setEnabled(false);
			CalcWindow.button_rightparenthesis.setEnabled(false);
			buffer = new StringBuffer("0");
			CalcWindow.textBuffer = new StringBuffer();
			CalcWindow.lab.setText("0");
		}
	}
		
}