java实现字符串四则运算公式解析工具类的方法

项目中用到用户定义运算公式进行就算的需求，这样需要进行字符串四则运算解析，下面提供字符串公式四则运算解析与计算工具类，需要的同学可参考。

工具类如下：FormulaCalculator.java：

package org.nercita.bcp.record.util;

import java.util.ArrayList;
import java.util.LinkedList;

/**
 * @author zhangwenchao
 * @since 2016-08-26
 * 公式计算的工具类
 */
public class FormulaCalculator {

	private static boolean isRightFormat = true;

	public static double getResult(String formula){
		double returnValue = 0;
		try{
			returnValue = doAnalysis(formula);
		}catch(NumberFormatException nfe){
			System.out.println("公式格式有误，请检查:" + formula);
		}catch(Exception e){
			e.printStackTrace();
		}
		if(!isRightFormat){
			System.out.println("公式格式有误，请检查:" + formula);
		}
		return returnValue;
	}

	private static double doAnalysis(String formula){
		double returnValue = 0;
		LinkedList<Integer> stack = new LinkedList<Integer>();
		int curPos = 0;
		String beforePart = "";
		String afterPart = "";
		String calculator = "";
		isRightFormat = true;
		while(isRightFormat&&(formula.indexOf('(') >= 0||formula.indexOf(')') >= 0)){
			curPos = 0;
			for(char s : formula.toCharArray()){
				if(s == '('){
					stack.add(curPos);
				}else if(s == ')'){
					if(stack.size() > 0){
						beforePart = formula.substring(0, stack.getLast());
						afterPart = formula.substring(curPos + 1);
						calculator = formula.substring(stack.getLast() + 1, curPos);
						formula = beforePart + doCalculation(calculator) + afterPart;
						stack.clear();
						break;
					}else{
						System.out.println("有未关闭的右括号！");
						isRightFormat = false;
					}
				}
				curPos++;
			}
			if(stack.size() > 0){
				System.out.println("有未关闭的左括号！");
				break;
			}
		}
		if(isRightFormat){
			returnValue = doCalculation(formula);
		}
		return returnValue;
	}

	private static double doCalculation(String formula) {
		ArrayList<Double> values = new ArrayList<Double>();
		ArrayList<String> operators = new ArrayList<String>();
		int curPos = 0;
		int prePos = 0;
		int minus = 0;
		for (char s : formula.toCharArray()) {
			 if ((s == '+' || s == '-' || s == '*' || s == '/') && minus !=0 && minus !=2) {
				 values.add(Double.parseDouble(formula.substring(prePos, curPos).trim()));
				 operators.add("" + s);
				 prePos = curPos + 1;
				 minus = minus +1;
			 }else{
				 minus =1;
			 }
			 curPos++;
		}
		values.add(Double.parseDouble(formula.substring(prePos).trim()));
		char op;
		for (curPos = 0; curPos <= operators.size() - 1; curPos++) {
			op = operators.get(curPos).charAt(0);
			switch (op) {
			case '*':
				values.add(curPos, values.get(curPos) * values.get(curPos + 1));
				values.remove(curPos + 1);
				values.remove(curPos + 1);
				operators.remove(curPos);
				curPos = -1;
				break;
			case '/':
				values.add(curPos, values.get(curPos) / values.get(curPos + 1));
				values.remove(curPos + 1);
				values.remove(curPos + 1);
				operators.remove(curPos);
				curPos = -1;
				break;
			}
		}
		for (curPos = 0; curPos <= operators.size() - 1; curPos++) {
			op = operators.get(curPos).charAt(0);
			switch (op) {
			case '+':
				values.add(curPos, values.get(curPos) + values.get(curPos + 1));
				values.remove(curPos + 1);
				values.remove(curPos + 1);
				operators.remove(curPos);
				curPos = -1;
				break;
			case '-':
				values.add(curPos, values.get(curPos) - values.get(curPos + 1));
				values.remove(curPos + 1);
				values.remove(curPos + 1);
				operators.remove(curPos);
				curPos = -1;
				break;
			}
		}
		return values.get(0).doubleValue();
	}

	public static void main(String[] args) {
		System.out.println(FormulaCalculator.getResult("3-(4*5)+5"));
		System.out.println(FormulaCalculator.getResult("7/2-(-4)"));
		System.out.println(FormulaCalculator.getResult("1287763200000-1276272000000")/(3600*24*1000));
	}

}

支持四则运算，同时支持负数解析。

另附，小数数据保留位数工具类，SetNumberPrecision.java

package org.nercita.bcp.record.util;

import java.text.DecimalFormat;

/**

 * @author zhangwenchao
 * 小数点 精度的工具类
 */
public class SetNumberPrecision {

	public static String setNumberPrecision(double x,int Number){
		String p="#########0";
		if(Number==0){
			p="#########0";
		}else{
			p="#########0.";
			for(int i=0;i<Number;i++){//for的巧妙运用
				p=p+"0";
			}
		}
		DecimalFormat f = new DecimalFormat(p);
		String s = f.format(x).toString();
		return s;
	}

}

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