Hi Rahul,
Assuming that
String domainnames[] contains list of previously selected domain Ids, then to check the previously selected domain you have to try out
<c:forEach var="domain" items="${domainmap}">
<tr><td>
<input type=checkbox name=selecteddomains value="${domain.value.domainName}"
<c:forEach var="domainId" items="${domainnames}">
<c:if test="${domainId==domain.value.domainId}">
checked="checked"
</c:if>
</c:forEach>
/> //close of input
Please verify syntax from your side, its been long I have worked on JSTL, but you can follow the logic
<c: out value="${domain.value.domainName}" ></c: out>
<c: out value="${domain.value.domainId}"></c: out>
</td></tr>
</c:forEach>