最近想把这破机 装成WIN7 想想还是算了 ...  反正用的机会也不多。

不过 发现了一些 想念的东西

从前的作业.

从前的记忆.

package org.lmz;import java.util.Queue;import java.util.Scanner;import java.util.Stack;import java.util.concurrent.LinkedBlockingQueue;public class calculator_test {	static String operator = "+-*/%^()";	/**	 * 预处理表达式，正、负号前加0(如果一个加号（减号）出现在最前面或左括号后面，则该加号（减号）为正负号)  比如  -1-(-1+1) 这种表达式 会处理成 0-1-(0-1+1)	 */	public static String pretreatment(String str) {		StringBuffer sb = new StringBuffer(str);		for (int i = 0; i < sb.length(); i++) {			char c = sb.charAt(i);			if (operator.indexOf(c) >= 0) {				if (i == 0) {					sb.insert(0, '0');					i++;				} else if (sb.charAt(i - 1) == '(') {					sb.insert(i, '0');					i++;				}			}		}		return sb.toString();	}	/***	 * 0 优先级相等 ； -1 op1 优先级大于op2； 1 op2 优先级大于 op1	 */	public static int opcompare(char op1, char op2) {		if (op1 == '(') { // 遇到括号 就直接入栈 所以 op2 大			return 1;		}		if ('^' == op1) {			if (op2 == '^') {				return 0;			}			return -1;		} else if ("+-".indexOf(op1) >= 0) {			if ("+-".indexOf(op2) >= 0) {				return 0;			}			return 1;		} else // if("*/%".indexOf(op1) >=0) 没必要 再判断是否为 */% 了		{			if ("+-".indexOf(op2) >= 0) {				return -1;			} else if ('^' == op2) {				return 1;			}			return 0;		}	}	/**	 * 计算传入的算术表达式 	 */	public static double Calculator2(String s) throws Exception {		//预处理式子		String prestr = pretreatment(s);		//用于保存  逆波兰式 的队列 		LinkedBlockingQueue
    
      polish = new LinkedBlockingQueue
     
      ();		// 拼接 数字 char ---> numble		StringBuffer temp = new StringBuffer();				Stack
      
        stack = new Stack
       
        ();		for (int i = 0; i < prestr.length(); i++) {			char c = prestr.charAt(i);			//如果找到 操作符			if (operator.indexOf(c) >= 0) {				if (temp.length() > 0) {//如果 有数字 就压栈					polish.offer(temp.toString());					temp = new StringBuffer();				}				switch (c) {				case '(':					stack.push(c);					break;				case ')':					while (stack.size() > 0) {						char op = stack.pop();						if (op != '(') {							polish.offer(String.valueOf(op));						} else {							break;						}					}					break;				default:					if (stack.size() == 0) {						stack.push(c);					} else {						while (stack.size() > 0) {							char op1 = stack.lastElement();							int com = opcompare(op1, c);							if (com <= 0) {								polish.offer(String.valueOf(stack.pop()));							} else {								stack.push(c);								break;							}						}						if (stack.size() == 0) {							stack.push(c);						}					}					break;				}			} else {				temp.append(c);			}		}		if (temp.length() > 0) {			polish.offer(temp.toString());		}		while (stack.size() > 0) {			polish.offer(String.valueOf(stack.pop()));		}		System.out.println("Calcstra Queue:" + polish.toString());		return CalcstraWithQueue(polish);	}	/**	 *  计算 逆波兰表达式  用队列表示	 * @throws Exception  各种错误都有可能	 */	public static double CalcstraWithQueue(Queue
        
          que) throws Exception {		Stack
         
           stack = new Stack
          
           (); while(true) { String str = que.poll(); if(str == null) { break; } if (operator.indexOf(str) >= 0) { double num2 = stack.pop(); double num1 = stack.pop(); double tempresult = 0; switch (str.charAt(0)) { case '+': tempresult = num1 + num2; break; case '-': tempresult = num1 - num2; break; case '*': tempresult = num1 * num2; break; case '/': if(num2 == 0) { throw new Exception("出错:除数为 0"); } tempresult = num1 / num2; break; case '%': tempresult = num1 % num2; break; case '^': tempresult = Math.pow(num1, num2); break; default: throw new Exception("运算符: " + str + " 未识别!"); } stack.push(tempresult); } else { stack.push(Double.valueOf(str)); } } return stack.pop(); } public static void main(String[] args) { Scanner reader = new Scanner(System.in); while(true) { String s = reader.nextLine(); double result = 0; try { result = Calculator2(s); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println(result); } }}