java - JSTL forEach reverse order

Question

Using JSTL's forEach tag, is it possible to iterate in reverse order?

Answer 1

When you are using forEach to create an integer loop, you can go forward or backward, but it requires some work. It turns out you cannot do this, for example:

<c:forEach var="i" begin="10" end="0" step="-1">
    ....
</c:forEach>

because the spec requires the step is positive. But you can always loop in forward order and then use <c:var to convert the incrementing number into a decrementing number:

<c:forEach var="i" begin="0" end="10" step="1">
   <c:var var="decr" value="${10-i}"/>
    ....
</c:forEach>

However, when you are doing a forEach over a Collection of any sort, I am not aware of any way to have the objects in reverse order. At least, not without first sorting the elements into reverse order and then using forEach.

I have successfully navigated a forEach loop in a desired order by doing something like the following in a JSP:

<%
List list = (List)session.getAttribute("list");
Comparator comp = ....
Collections.sort(list, comp);
%>


<c:forEach var="bean" items="<%=list%>">
     ...
</c:forEach>

With a suitable Comparator, you can loop over the items in any desired order. This works. But I am not aware of a way to say, very simply, iterate in reverse order the collection provided.