java解析四则运算+-*/()字符串表达式,并按照精度进行计算结果,还提供按精度比较的方法
前言：最近涉及到业务人员配置数学表达式，要求解析并按照精度进行计算
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参考了如下百度百科对逆波兰算法的讲解进行开发，开发过程中还参考了一篇精度算法的文章
1：http://baike.baidu.com/view/552648.htm
2：还有一遍文章忘了链接了，如果侵犯作者权利请告知，我立即删除
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该类支持精度计算，支持负数，精度比较等功能。计算按照逆波兰方式解析。
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/** * @Project: BizRule * @File: org.coffeesweet.util.MathExpress.java * @Author: coffeesweet * @Date: 2011-3-28 * @Description: 2011 coffeesweet Inc. All rights reserved. */package org.coffeesweet.util;import java.math.BigDecimal;import java.math.MathContext;import java.math.RoundingMode;import java.util.ArrayList;import java.util.LinkedList;import java.util.List;import java.util.StringTokenizer;import java.util.regex.Matcher;import java.util.regex.Pattern;/** * @author coffeesweet * +,-,*,/四则运算的表达式逆波兰解析计算类,精确计算,应用BigDecimal类处理 * 支持负数,但规范除整个表达式第一个数为负数时可以不出现在'('后，其它表达式中间任何位置的 * 负数必须出现在'('后,即：用括号括起来。比如：-3+(-2+1)*10或-3+((-2)+1)*10或(-3)+(-2+1)*10或(-3)+((-2)+1)*10 */public class MathExpress {/** * + */ private final static String OP1 = "+"; /** * - */ private final static String OP2 = "-"; /** * * */ private final static String OP3 = "*"; /** * / */ private final static String OP4 = "/"; /** * ^ */// private final static String OP5 = "^"; /** * % */// private final static String OP6 = "%"; /** * ( */ private final static String OPSTART = "("; /** * ) */ private final static String OPEND = ")"; /** * !用来替代负数前面的'-' */// private final static String NEGATIVESING = "!"; /** * !用来替代负数前面的'+' */// private final static String PLUSSING = "@"; /** * '#'用来代表运算级别最低的特殊字符 */// private final static String LOWESTSING = "#"; //最原始的四则运算式 private String expBase; //经过初始化处理后的四则运算式 private String expInited; //精度 private int precision=10; //取舍模式 private RoundingMode roundingMode=RoundingMode.HALF_UP; //精度上下文 private MathContext mc; //四则运算解析 private List<String> expList = new ArrayList<String>(); //存放逆波兰表达式 private List<String> rpnList = new ArrayList<String>(); public MathExpress(){ } public MathExpress(String expBase) { init(expBase,this.precision,this.roundingMode);}public MathExpress(String expBase,int precision,RoundingMode roundingMode){ init(expBase,precision,roundingMode); } public void init(String expBase,int precision,RoundingMode roundingMode){ this.expBase = expBase; this.precision = precision; this.roundingMode = roundingMode; this.mc = new MathContext(precision,roundingMode); this.expInited = initExpress(expBase); StringTokenizer st = new StringTokenizer(this.expInited,"+-*/^%()",true); while(st.hasMoreElements()){ this.expList.add(st.nextElement().toString().trim()); } this.rpnList = initRPN(this.expList); } /** * @return the expBase */public String getExpBase() {return expBase;}/** * @param expBase the expBase to set */public void setExpBase(String expBase) {this.expBase = expBase;}/** * @return the expInited */public String getExpInited() {return expInited;}/** * @param expInited the expInited to set */public void setExpInited(String expInited) {this.expInited = expInited;}/** * @return the precision */public int getPrecision() {return precision;}/** * @param precision the precision to set */public void setPrecision(int precision) {this.precision = precision;}/** * @return the roundingMode */public RoundingMode getRoundingMode() {return roundingMode;}/** * @param roundingMode the roundingMode to set */public void setRoundingMode(RoundingMode roundingMode) {this.roundingMode = roundingMode;}/** * @return the expList */public List<String> getExpList() {return expList;}/** * @param expList the expList to set */public void setExpList(List<String> expList) {this.expList = expList;}/** * @return the rpnList */public List<String> getRpnList() {return rpnList;}/** * @param rpnList the rpnList to set */public void setRpnList(List<String> rpnList) {this.rpnList = rpnList;}/** * @return the mc */public MathContext getMc() {return mc;}/** * @param mc the mc to set */public void setMc(MathContext mc) {this.mc = mc;}/** * 去除空白字符和在负号'-'前加'0',便于后面的StringTokenizer * @param exp * @return */ private static String initExpress(String exp){ String reStr = null; reStr = exp.replaceAll("\\s", ""); if(reStr.startsWith("-")){ reStr = "0"+reStr; } reStr = reStr.replaceAll("\\(\\-", "(0-"); return reStr; } /** * 是否是整数或是浮点数,但默认-05.15这种也认为是正确的格式 * @param str * @return */ private boolean isNumber(String str){ Pattern p = Pattern.compile("^(-?\\d+)(\\.\\d+)?$"); Matcher m = p.matcher(str); boolean isNumber = m.matches(); return isNumber; } /** * 设置优先级顺序()设置与否无所谓 * @param sign * @return */ private int precedence(String str){ char sign = str.charAt(0); switch(sign){ case '+': case '-': return 1; case '*': case '/': return 2; case '^': case '%': return 3; case '(': case ')':// case '#': default: return 0; } } /** * 转变为逆波兰表达式 * @param strList * @return */ public List<String> initRPN(List<String> strList){ List<String> returnList = new ArrayList<String>(); //用来存放操作符的栈 Stack stack = new Stack();// stack.push(LOWESTSING); int length = strList.size(); for(int i=0;i<length;i++ ){ String str = strList.get(i); if(isNumber(str)){ returnList.add(str); }else{ if(str.equals(OPSTART)){ //'('直接入栈 stack.push(str); }else if(str.equals(OPEND)){ //')' //进行出栈操作，直到栈为空或者遇到第一个左括号 while (!stack.isEmpty()) { //将栈顶字符串做出栈操作 String tempC = stack.pop(); if (!tempC.equals(OPSTART)) { //如果不是左括号，则将字符串直接放到逆波兰链表的最后 returnList.add(tempC); }else{ //如果是左括号，退出循环操作 break; } } }else{ if (stack.isEmpty()) { //如果栈内为空 //将当前字符串直接压栈 stack.push(str); }else{ //栈不空,比较运算符优先级顺序 if(precedence(stack.top())>=precedence(str)){ //如果栈顶元素优先级大于当前元素优先级则 while(!stack.isEmpty() && precedence(stack.top())>=precedence(str)){ returnList.add(stack.pop()); } } stack.push(str); } } } } //如果栈不为空，则将栈中所有元素出栈放到逆波兰链表的最后 while (!stack.isEmpty()) { returnList.add(stack.pop()); } return returnList; } /** * 计算逆波兰表达式 * @param rpnList * @return */ public String caculate(List<String> rpnList){ Stack numberStack = new Stack(); int length=rpnList.size(); for(int i=0;i<length;i++){ String temp=rpnList.get(i); if(isNumber(temp)){ numberStack.push(temp); }else{ BigDecimal tempNumber1 = new BigDecimal(numberStack.pop(),this.mc); BigDecimal tempNumber2 = new BigDecimal(numberStack.pop(),this.mc); BigDecimal tempNumber = new BigDecimal("0",this.mc); if(temp.equals(OP1)){ tempNumber=tempNumber2.add(tempNumber1); }else if(temp.equals(OP2)){ tempNumber=tempNumber2.subtract(tempNumber1); }else if(temp.equals(OP3)){ tempNumber=tempNumber2.multiply(tempNumber1); }else if(temp.equals(OP4)){ tempNumber=tempNumber2.divide(tempNumber1, precision, roundingMode); } numberStack.push(tempNumber.toString()); } } return numberStack.pop(); } /** * 按照类的缺省参数进行计算 * @return */ public String caculate(){ return caculate(this.rpnList); } /** * 数字条件表达式精确比较 * eg: "3.0>2" "1<5" "1==5" "1!=5" "(1.0+2)>3" "((-0.9+3)>=2. 1)" * 不支持&&,||等连接符 * @param str * @return */ public static boolean compareTo(String strParm){ boolean reBoolean = false; boolean isParentheses = false;//标记是否有()括上整个字符串 String str = initExpress(strParm); Pattern p = Pattern.compile("^\\([\\s\\S]*\\)$"); Matcher m = p.matcher(str); isParentheses = m.matches(); if(-1==str.indexOf(">=")&&-1==str.indexOf("<=")&&-1==str.indexOf("==")&&-1==str.indexOf("!=")){ if(-1==str.indexOf(">")&&-1==str.indexOf("<")) throw new IllegalArgumentException("异常:条件表达式不正确!"); } if(-1 != str.indexOf(">=")){ String[] strTemps = str.split(">="); if(isParentheses){ strTemps[0] = strTemps[0] + ")"; strTemps[1] = "(" + strTemps[1]; } int r = new BigDecimal((new MathExpress(strTemps[0]).caculate())).compareTo(new BigDecimal((new MathExpress(strTemps[1]).caculate()))); if( -1 == r ){ reBoolean = false; }else{ reBoolean = true; } }else if(-1 != str.indexOf("<=")){ String[] strTemps = str.split("<="); if(isParentheses){ strTemps[0] = strTemps[0] + ")"; strTemps[1] = "(" + strTemps[1]; } int r = new BigDecimal((new MathExpress(strTemps[0]).caculate())).compareTo(new BigDecimal((new MathExpress(strTemps[1]).caculate()))); if( 1 == r ){ reBoolean = false; }else{ reBoolean = true; } }else if(-1 != str.indexOf("==")){ String[] strTemps = str.split("=="); if(isParentheses){ strTemps[0] = strTemps[0] + ")"; strTemps[1] = "(" + strTemps[1]; } int r = new BigDecimal((new MathExpress(strTemps[0]).caculate())).compareTo(new BigDecimal((new MathExpress(strTemps[1]).caculate()))); if( 0 == r ){ reBoolean = true; }else{ reBoolean = false; } }else if(-1 != str.indexOf("!=")){ String[] strTemps = str.split("!="); if(isParentheses){ strTemps[0] = strTemps[0] + ")"; strTemps[1] = "(" + strTemps[1]; } int r = new BigDecimal((new MathExpress(strTemps[0]).caculate())).compareTo(new BigDecimal((new MathExpress(strTemps[1]).caculate()))); if( 0 != r ){ reBoolean = true; }else{ reBoolean = false; } }else if((-1 != str.indexOf(">")) && (-1 == str.indexOf("="))){ String[] strTemps = str.split(">"); if(isParentheses){ strTemps[0] = strTemps[0] + ")"; strTemps[1] = "(" + strTemps[1]; } int r = new BigDecimal((new MathExpress(strTemps[0]).caculate())).compareTo(new BigDecimal((new MathExpress(strTemps[1]).caculate()))); if( 1 == r ){ reBoolean = true; }else{ reBoolean = false; } }else if((-1 != str.indexOf("<")) && (-1 == str.indexOf("="))){ String[] strTemps = str.split("<"); if(isParentheses){ strTemps[0] = strTemps[0] + ")"; strTemps[1] = "(" + strTemps[1]; } int r = new BigDecimal((new MathExpress(strTemps[0]).caculate())).compareTo(new BigDecimal((new MathExpress(strTemps[1]).caculate()))); if( -1 == r ){ reBoolean = true; }else{ reBoolean = false; } } return reBoolean; } public static void main(String...args){// MathExpress me = new MathExpress("-(-0.5+0.1)*10+2",10,RoundingMode.HALF_UP);// System.out.println(me.getExpList());// List<String> tempList = me.initRPN(me.getExpList());// System.out.println(tempList);// String resultStr = me.caculate(tempList);// System.out.println(resultStr); MathExpress me = new MathExpress("-(-1.5000000003+0.1)*10+2"); String resultStr = me.caculate(); BigDecimal bd = new BigDecimal(resultStr); BigDecimal bd2 = bd.setScale(2, RoundingMode.HALF_UP); System.out.println(me.caculate()); System.out.println(bd.toString()); System.out.println(bd.scale()); System.out.println(bd2.toString()); System.out.println(bd2.scale()); // System.out.println("------------------------------------");// Pattern p = Pattern.compile("^\\([\\s\\S]*\\)$");//匹配类似以'('开头')'结尾的字符串// Matcher m = p.matcher("(2. 0>2.22)");// System.out.println(m.matches()); boolean reBoolean = MathExpress.compareTo("((-8.0+3)>=2. 1)"); System.out.println(reBoolean); } /** * 栈 */ private class Stack { LinkedList<String> stackList = new LinkedList<String>(); public Stack() { } /** * 入栈 * @param expression */ public void push(String expression) { stackList.addLast(expression); } /** * 出栈 * @return */ public String pop() { return stackList.removeLast(); } /** * 栈顶元素 * @return */ public String top() { return stackList.getLast(); } /** * 栈是否为空 * @return */ public boolean isEmpty() { return stackList.isEmpty(); } }}?