计算（输入计算式得出结果）

算式得出结果）"/>

计算（输入计算式得出结果）

计算器 

一、封装类

public static void main(String[] args) throws Exception {
ScriptEngine js = new ScriptEngineManager().getEngineByName("JavaScript");
System.out.println(js.eval("(-2+3*5) + 30*10%".replaceAll("%","/100")));
}

二、原创计算器工具类

package com;import java.math.BigDecimal;
import java.util.LinkedList;
import java.util.List;public class Calculate {public static void main(String[] args) throws Exception{System.out.println(getResult("-2+3*5"));}private static String getResult(String formula) throws Exception{formula = formula.replace("（","(");formula = formula.replace("）",")");String reg = "[0-9\\\\.*%+()/-]*";if(!formula.matches(reg)){return "";}int leftCount = 0;int rightCount = 0;for(int i=0;i<formula.length();i++){int left = formula.indexOf("(",i);if(left!=-1){leftCount++;i = left;}else{break;}}for(int i=0;i<formula.length();i++){int right = formula.indexOf(")",i);if(right!=-1){rightCount++;i = right;}else{break;}}if(leftCount!=rightCount){return "";}String formulaResult = formula;formulaResult = getBrackets(formulaResult);formulaResult = formulaResult.replace(formulaResult, getResultDetail(formulaResult));return new BigDecimal(formulaResult).setScale(2,BigDecimal.ROUND_HALF_UP).toString();}//处理表达式小括号public static String getBrackets(String formula) throws Exception{if(formula.contains("(")){int left = formula.lastIndexOf("(");int right = formula.indexOf(")",left);String formulaTemp = formula.substring(left,right+1);String result = getResultDetail(formulaTemp);formula = formula.replace(formulaTemp,result);formula = getBrackets(formula);}return formula;}//计算表达式public static String getResultDetail(String formula) throws Exception{formula = formula.replace("(","");formula = formula.replace(")","");//处理百分号List<Integer> percentList = new LinkedList<Integer>();for(int i=0;i<formula.length();i++){int percent = formula.indexOf("%",i);if(percent!=-1){percentList.add(percent);i=percent;}else{break;}}String formulaTemp = formula;for(int i=0;i<percentList.size();i++){String percentNum = formula.substring(0,percentList.get(i));int sub = percentNum.lastIndexOf("-");int add = percentNum.lastIndexOf("+");int mul = percentNum.lastIndexOf("*");int div = percentNum.lastIndexOf("/");int num = Integer.max(Integer.max(Integer.max(sub,add),mul),div);String numStr = formula.substring(num+1,percentList.get(i));formulaTemp = formulaTemp.replace(numStr+"%",new BigDecimal(numStr).multiply(new BigDecimal("0.01")).setScale(4,BigDecimal.ROUND_HALF_UP).toString());}formula = formulaTemp;String formulaResult = formula;formulaResult = calculateFirst(formulaResult);formulaResult = calculateSecond(formulaResult);return formulaResult;}//计算表达式所有乘除public static String calculateFirst(String formula) throws Exception{if(hasFirst(formula)){formula = getFirst(formula);formula = calculateFirst(formula);}return formula;}//计算表达式所有加减public static String calculateSecond(String formula) throws Exception{if(hasSecond(formula)){formula = getSecond(formula);formula = calculateSecond(formula);}return formula;}//判断表达式是否有乘除public static boolean hasFirst(String formula) throws Exception{int mul = formula.indexOf("*");int div = formula.indexOf("/");int max = Integer.max(mul,div);boolean flag = false;if(max != -1){flag = true;}return flag;}//判断表达式是否有加减public static boolean hasSecond(String formula) throws Exception{int sub = formula.indexOf("-")==0?formula.indexOf("-",1):formula.indexOf("-");int add = formula.indexOf("+");int max = Integer.max(sub,add);boolean flag = false;if(max != -1){flag = true;}return flag;}//算表达式乘除，返回之后的表达式public static String getFirst(String formula) throws Exception{int mul = formula.indexOf("*");int div = formula.indexOf("/");int min = Integer.min(mul,div);min = min==-1?Integer.max(mul,div):min;String formulaResult = formula;List<String > list = getFormula(formula,min);BigDecimal result = bigDecimalCal(new BigDecimal(list.get(1)),new BigDecimal(list.get(2)),list.get(0).charAt(0));formulaResult = formulaResult.replace(list.get(1) + list.get(0) + list.get(2), result.toString());return formulaResult;}//算表达式加减，返回之后的表达式public static String getSecond(String formula) throws Exception{int sub = formula.indexOf("-")==0?formula.indexOf("-",1):formula.indexOf("-");int add = formula.indexOf("+");int min = Integer.min(sub,add);min = min==-1?Integer.max(sub,add):min;String formulaResult = formula;List<String > list = getFormula(formula,min);BigDecimal result = bigDecimalCal(new BigDecimal(list.get(1)),new BigDecimal(list.get(2)),list.get(0).charAt(0));formulaResult = formulaResult.replace(list.get(1) + list.get(0) + list.get(2), result.toString());return formulaResult;}//找出两个参数及运算符public static List<String> getFormula(String formula, int n) throws Exception{List<String> list = new LinkedList<String>();list.add(formula.charAt(n) + "");String leftStr = formula.substring(0,n);String rightStr = formula.substring(n+1);int leftSub = leftStr.lastIndexOf("-");int leftAdd = leftStr.lastIndexOf("+");int leftMul = leftStr.lastIndexOf("*");int leftDiv = leftStr.lastIndexOf("/");int leftNum = Integer.max(Integer.max(Integer.max(leftSub,leftAdd),leftMul),leftDiv);list.add(formula.substring(leftNum==0?leftNum:leftNum+1,n));int rightSub = rightStr.lastIndexOf("-")==0?rightStr.indexOf("-",1):rightStr.indexOf("-");int rightAdd = rightStr.lastIndexOf("+");int rightMul = rightStr.lastIndexOf("*");int rightDiv = rightStr.lastIndexOf("/");int rightNum = -1;List<Integer> rightList = new LinkedList<Integer>();if(rightSub!=-1){rightList.add(rightSub);}if(rightAdd!=-1){rightList.add(rightAdd);}if(rightMul!=-1){rightList.add(rightMul);}if(rightDiv!=-1){rightList.add(rightDiv);}for(int i=0;i<rightList.size();i++){if(rightNum == -1){rightNum = rightList.get(i);}else if(rightList.get(i)<rightNum){rightNum = rightList.get(i);}}list.add(formula.substring(n+1,rightNum == -1?formula.length():n+1+rightNum));return list;}//计算制定两个参数及运算符public static BigDecimal bigDecimalCal(BigDecimal a1, BigDecimal a2, char operator) throws Exception{switch (operator){case '+':return a1.add(a2);case '-':return a1.subtract(a2);case '*':return a1.multiply(a2);case '/':return a1.divide(a2,20,BigDecimal.ROUND_HALF_UP);default:break;}throw new Exception("illegal operator!");}}