Manipulating Hashtable key is not working

Question

I am trying to access a Hashtables value based on its key, which is a number as String in JSTL. But if I increment/decrement the keys value, it does not work anymore.

I iterate the sorted list of keys in a for loop. I use this item to access Hashtable.

<c:forEach items="${helper:getSortedList(hashtableObj)}" var="lineNumber" varStatus="loop">
    <c:if test="${param.lineNbr eq lineNumber}">
        <c:if test="${lineNumber>1}">
            <fmt:parseNumber var="prevLineNumberKey" type="number" value="${lineNumber-1}" />
            <c:out value="PREV ${hashtableObj[prevLineNumberKey]}" escapeXml="false"/><br/>
        </c:if>
        <c:out value="Current :${lineNumber}" /><br/>
        <c:if test="${lineNumber<fn:length(hashtableObj)-1}">
            <fmt:parseNumber var="nextLineNumberKey" type="number" value="${lineNumber+1}" />
            <c:out value="NEXT ${hashtableObj[nextLineNumberKey+1]}" escapeXml="false"/><br/>
        </c:if>
</c:if>
</c:forEach>

The output is

PREV
Current :51
NEXT

But what I expected is

PREV 50
Current :51
NEXT 52

Any pointers are appreciated.

Answer 1

If keys in your Map is String than to get an element you must query it with String value. Your current solution queries a Map with Long value.
You can convert number to String and then query a Map like this:

<c:set var="numberAsString">${50 - 1}</c:set>
<c:out value="value: ${hashtableObj[numberAsString]}"/>