java 逆波兰表达式

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

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<String> polish = new LinkedBlockingQueue<String>();// 拼接 数字 char ---> numbleStringBuffer temp = new StringBuffer();Stack<Character> stack = new Stack<Character>();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<String> que) throws Exception {Stack<Double> stack = new Stack<Double>();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 blocke.printStackTrace();}System.out.println(result);}}}