四则运算（小清新）
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<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html > <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>你真棒</title> <style type="text/css"> body { background-image: url(start.jpg); background-size:1200px 700px; text-align:center; } </style> </head> <body> <div style="text-align: center; font-family: 微软雅黑; font-size: 50px; color: #C03; "><strong><em>四则运算</em></strong></div> <div style="text-align: center; font-family: 微软雅黑; font-size: 15px; color: #C03; "><strong><em>Welcome To User The System</em></strong></div> <br/> <form name="form1" method="post" action="arithmetic.jsp" > <blockquote> <blockquote> <blockquote> <blockquote> <blockquote> <blockquote> <blockquote> <blockquote> <blockquote> <blockquote> <div style="color: #C03"> <p>选择题目类型： <input name="elementNum" value="2" type="radio" />2元运算 <input name="elementNum" value="3" type="radio" checked="checked"/>3元运算<br><br> <strong>题目数量： <select name="count"> <option>10</option> <option>20</option> <option>30</option> <option>40</option> <option>50</option> <option>60</option> </select> <br /><br /> 限定时间： <select name="timelimit"> <option>1</option> <option>2</option> <option>3</option> <option>4</option> <option>5</option> <option>6</option> </select> 分钟 <br /> <input name="" type="submit" value="开始答题" style="margin:0 auto;display:block;" /> </strong> </p> </div> </blockquote> </blockquote> </blockquote> </blockquote> </blockquote> </blockquote> </blockquote> </blockquote> </blockquote> </blockquote> </form> </body> </html>
public class Arithmetic {
public static void main(String args[]){
System.out.println(arithmetic("2.2+((3+4)*2-22)/2*3.2"));
}
public static double arithmetic(String exp){
String result = parseExp(exp).replaceAll("[\\[\\]]", "");
return Double.parseDouble(result);
}
/**
* 解析计算四则运算表达式，例：2+((3+4)*2-22)/2*3
*/
public static String parseExp(String expression){
//String numberReg="^((?!0)\\d+(\\.\\d+(?<!0))?)|(0\\.\\d+(?<!0))$";
expression=expression.replaceAll("\\s+", "").replaceAll("^\\((.+)\\)$", "$1");
String checkExp="\\d";
String minExp="^((\\d+(\\.\\d+)?)|(\\[\\-\\d+(\\.\\d+)?\\]))[\\+\\-\\*\\/]((\\d+(\\.\\d+)?)|(\\[\\-\\d+(\\.\\d+)?\\]))$";
//最小表达式计算
if(expression.matches(minExp)){
String result=calculate(expression);
return Double.parseDouble(result)>=0?result:"["+result+"]";
}
//计算不带括号的四则运算
String noParentheses="^[^\\(\\)]+$";
String priorOperatorExp="(((\\d+(\\.\\d+)?)|(\\[\\-\\d+(\\.\\d+)?\\]))[\\*\\/]((\\d+(\\.\\d+)?)|(\\[\\-\\d+(\\.\\d+)?\\])))";
String operatorExp="(((\\d+(\\.\\d+)?)|(\\[\\-\\d+(\\.\\d+)?\\]))[\\+\\-]((\\d+(\\.\\d+)?)|(\\[\\-\\d+(\\.\\d+)?\\])))";
if(expression.matches(noParentheses)){
Pattern patt=Pattern.compile(priorOperatorExp);
Matcher mat=patt.matcher(expression);
if(mat.find()){
String tempMinExp=mat.group();
expression=expression.replaceFirst(priorOperatorExp, parseExp(tempMinExp));
}else{
patt=Pattern.compile(operatorExp);
mat=patt.matcher(expression);
if(mat.find()){
String tempMinExp=mat.group();
expression=expression.replaceFirst(operatorExp, parseExp(tempMinExp));
}
}
return parseExp(expression);
}
//计算带括号的四则运算
String minParentheses="\\([^\\(\\)]+\\)";
Pattern patt=Pattern.compile(minParentheses);
Matcher mat=patt.matcher(expression);
if(mat.find()){
String tempMinExp=mat.group();
expression=expression.replaceFirst(minParentheses, parseExp(tempMinExp));
}
return parseExp(expression);
}
/**
* 计算最小单位四则运算表达式（两个数字）
* @param exp
* @return
*/
public static String calculate(String exp){
exp=exp.replaceAll("[\\[\\]]", "");
String number[]=exp.replaceFirst("(\\d)[\\+\\-\\*\\/]", "$1,").split(",");
BigDecimal number1=new BigDecimal(number[0]);
BigDecimal number2=new BigDecimal(number[1]);
BigDecimal result=null;
String operator=exp.replaceFirst("^.*\\d([\\+\\-\\*\\/]).+$", "$1");
if("+".equals(operator)){
result=number1.add(number2);
}else if("-".equals(operator)){
result=number1.subtract(number2);
}else if("*".equals(operator)){
result=number1.multiply(number2);
}else if("/".equals(operator)){
result=number1.divide(number2);
}
return result!=null?result.toString():null;
}
}
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