《c:forEach 》表达式用法

https://blog.youkuaiyun.com/abou15871390117/article/details/66975963?locationNum=12&fps=1

* <c:forEach>（*****）
* 循环遍历数据（数组，集合，Map集合）
* 属性
var ：遍历数据的类型
items ：要遍历的内容

begin ：从哪开始
end ：到哪结束
step ：步长

varStatus：记录循环遍历的信息
* index
* count（常用）
* first
* last

* 代码
<%
String [] arrs = {"艾米1","艾米2","艾米3","艾米4"};
request.setAttribute("arrs", arrs);
%>
<!-- for(String s : arrs){ }  -->
<c:forEach var="s" items="${ arrs }">
${ s }
</c:forEach>


<h4>遍历集合</h4>
<%
List<String> list = new ArrayList<String>();
list.add("艾米1");
list.add("艾米2");
list.add("艾米3");
list.add("艾米4");
request.setAttribute("list", list);
%>
<c:forEach var="s" items="${ list }">
${ s }
</c:forEach>


<h4>遍历Map集合</h4>
<%
Map<String,String> map = new HashMap<String,String>();
map.put("aa", "美美");
map.put("bb", "小凤");
map.put("cc", "芙蓉");
request.setAttribute("map", map);
%>
<c:forEach var="entry" items="${ map }">
${ entry.key } -- ${ entry.value }
</c:forEach>

<h4>遍历对象的集合</h4>
<%
List<User> uList = new ArrayList<User>();
uList.add(new User("艾米1","123"));
uList.add(new User("艾米2","234"));
uList.add(new User("艾米3","345"));
request.setAttribute("uList", uList);
%>
<c:forEach var="user" items="${ uList }">
${ user.username } -- ${ user.password }
</c:forEach>


<h4>迭代数据</h4>
<h4>迭代从1到10</h4>
<c:forEach var="i" begin="1" end="10" step="2">
${ i }
</c:forEach>




<h4>计算从1加到100的和</h4>
<c:set var="sum" value="0" scope="page"></c:set>
<c:forEach var="i" begin="1" end="100" step="1">
<c:set var="sum" value="${ sum + i }"></c:set>
</c:forEach>
${ sum }

<h4>遍历10到100的偶数，每到第3个数，显示红色</h4>
<c:forEach var="i" begin="10" end="100" step="2" varStatus="status">
<c:choose>
<c:when test="${ status.first }">
<font color="blue">${ i }</font>
</c:when>
<c:when test="${ status.count % 3 eq 0 }">
<font color="red">${ i }</font>
</c:when>
<c:otherwise>
${ i }
</c:otherwise>
</c:choose>
</c:forEach>