四则运算（小清新）

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<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>
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<form  name="form1" method="post" action="arithmetic.jsp" >
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               <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
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                    <input name="" type="submit" value="开始答题" style="margin:0 auto;display:block;" />
                    
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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;
	}
}