我们在利用EL和JSTL在不同页面间获取值时，还可以利用EL中的运算符，对获取到的数值进行运算。
代码如下
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!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>四则运算</title>
</head>
<body>
//a与b是key值，两者value值分别为13和7
${a-b}<br/>
${a+b}<br/>
${a*b}<br/>
${a/b}<br/> //等同于${a div b}
${a % b}<br/> //等同于${a mod b}
------------------------------------------
//关系运算符
${a>b}<br/>
${a<b}<br/>
${a==b}<br/>
${a!=b}<br/>
${a==b?"相等","不相等"}<br/>
------------------------------------------
//empty对数组，集合进行判空
${empty lists}<br/>
------------------------------------------
//逻辑运算符,a b为key值，其数值类型为Boolean
${a && b}<br/>
${a || b}<br/>
${! b}<br/>
</body>
</html>