ELDemo1.java文件：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>EL运算</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<!--
<link rel="stylesheet" type="text/css" href="styles.css" target="_blank" rel="external nofollow" >
-->
</head>
<body>
<br/>------empty运算符--------<br/>
<%
pageContext.setAttribute("s1", "");
pageContext.setAttribute("s2", null);
List list = new ArrayList();
list.add("aa");
pageContext.setAttribute("list", list);
String strs[] = {};
pageContext.setAttribute("strs", strs);
%>
${empty s1}<br/>
${empty s2}<br/>
${empty list}<br/>
${empty strs}<br/>
<br/>------三元运算符--------<br/>
<%
pageContext.setAttribute("gender", "female");
%>
<input type="radio" name="gender" value="male" ${gender=='male'?'checked="checked"':''}/>男
<input type="radio" name="gender" value="female" ${gender=='female'?'checked="checked"':''}/>女
</body>
</html>
运行：http://localhost:8080/EL_project/ELDemo1.jsp
结果：
![EL表达式和JSTL的总结El表达式几个问题及答案[图]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)