package com.hostlemon.zhangyz.test;import java.math.BigDecimal;import java.util.Stack;/** * @author zhangyz * @since 2013-11-21 * @version 1.0.0 */public class J2SETest {/** * 常用加减乘除括号字符 */private static final String OPERATOR = "+-*/()";/** * 算法符号的优先级二维表 */private static int[][] OPERATORCOMPARE = new int[][] { { 0, 0, -1, -1, -1, 1 },{ 0, 0, -1, -1, -1, 1 }, { 1, 1, 0, 0, -1, 1 },{ 1, 1, 0, 0, -1, 1 }, { 1, 1, 1, 1, 0, 1 },{ -1, -1, -1, -1, -1, 0 } };/** * 特殊字符用于标记给定表达式结尾 */private static final char ENDCHAR='\n';/** * JAVA 执行入口 * * @param args */public static void main(String[] args) {println(OPERATOR, OPERATORCOMPARE);String solution = "((2*(19-13*(1+2)/39)/6+4)-5)/5+((2+3)*2-5)";System.out.println(solution+"="+calc(solution));}/** * @param solution */private static BigDecimal calc(String solution) {//需要给表达式添加结束符solution+=ENDCHAR;Stack<BigDecimal> digital = new Stack<BigDecimal>();Stack<Character> opeators = new Stack<Character>();int begin = 0;int length = 0;char current = 0;for (int i = 0; i < solution.length(); i++) {current = solution.charAt(i);//解析数字if (('0' <= current && current <= '9')||current=='.') {length++;continue;} else {//解析的数字压入数字栈if (length > 0) {digital.add(new BigDecimal(solution.substring(begin, begin + length)));begin += length;length = 0;}begin++;//如果扫描结束,但数字栈及符号栈还有数据需要计算,比如1+2+(1+3),不进行此步骤"[3, 4],[+]"为两个栈的元素if (ENDCHAR == current) { while(!opeators.isEmpty()){ operator(digital, opeators); }} else {//处理当前操作字符,无限循环,处理当前操作字符后跳出循环while (true) {if (opeators.isEmpty()) {opeators.push(current);break;} else {if (OPERATORCOMPARE[OPERATOR.indexOf(current)][OPERATOR.indexOf(opeators.lastElement())] > 0) {opeators.push(current);break;} else if (opeators.lastElement() == '('&& current == ')') {opeators.pop();break;} else if (opeators.lastElement() == '('&& current != ')') {opeators.push(current);break;} else {operator(digital, opeators);}}}}}}System.out.println(digital);System.out.println(opeators);return digital.pop();}/** * 从符号栈弹出一个符号,从数字栈弹出两个数字,进行数学运算并压入数字栈 * @param digital * @param opeators */private static void operator(Stack<BigDecimal> digital,Stack<Character> opeators) {BigDecimal number1=digital.pop();BigDecimal number2=digital.pop();switch (opeators.pop()) {case '+':digital.push(number2.add(number1));break;case '-':digital.push(number2.subtract(number1));break;case '*':digital.push(number2.multiply(number1));break;case '/':digital.push(number2.divide(number1,4,BigDecimal.ROUND_HALF_UP));break;}}/** * 打印符号优先级二维表 * * @param operator * @param operatorCompare */private static void println(String operator, int[][] operatorCompare) {System.out.print(" \t");for (int i = 0; i < operator.length(); i++) {System.out.print(operator.charAt(i));System.out.print('\t');}for (int i = 0; i < operatorCompare.length; i++) {System.out.println();System.out.print(operator.charAt(i));System.out.print('\t');for (int j = 0; j < operatorCompare[i].length; j++) {System.out.print(operatorCompare[i][j] == 0 ? '=': (operatorCompare[i][j] > 0 ? '>' : '<'));System.out.print('\t');}}System.out.println();}}
