Question

I have a problem here in JSTL, I have an array object coming from a request attribute that was set in a servlet. All I want to do is to print the indexes of the array. Any help please? Here’s the code:

<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@taglib uri="/WEB-INF/tlds/Functions" prefix="func"%>
<table>
    <tr>
        <td>
            <b>k</b> = 
        </td>
        <td>
            <table border="1">
                <c:forEach var="i" begin="0" end="${responseVector.length}">
                <tr>
                    <td>k<sub>${i}</sub></td><!-- I wish to print the indexes here -->
                </tr>
                </c:forEach>
            </table>
        </td>
        <td>
            <table border="1">
                <c:forEach var="i" items="${responseVector}">
                <tr>
                    <td>${func:roundOff(i, 4)}</td>
                </tr>
                </c:forEach>
            </table>
        </td>
    </tr>
</table>
<br/>

In the code above, responseVector is a double array object, but I want the variable i in the first loop to print the indexes of the array object each time the loop iterates. My expected output is: k0, k1, k2, … but am having an exception instead.

Answer 1

Try this: (Use varStatus attribute)

<c:forEach items="${responseVector}" var="r" varStatus="status">
  <c:out value="${status.index}"/>
</c:forEach>

${status.index} will give you:

Retrieves the index of the current round of the iteration. If
iteration is being performed over a subset of an underlying array,
java.lang.Collection, or other type, the index returned is absolute
with respect to the underlying collection. Indices are 0-based.

More info here.