Somar valores dentro de ForEach

<c:forEach var="contaapagar" items="<%=modelcontapagar.getAllNonPaid()%>">               
               <c:if test="${usrLogado.id eq contaapagar.idUsuario}">
               <tr valign="top">
                   <td>${contaapagar.id}</td>
                   <td>${contaapagar.credor}</td>
                   <td>${contaapagar.valor}</td>
                   <td>${contaapagar.desc}</td>
                   <td>${contaapagar.dataPagamento}</td>
                   <td>${contaapagar.dataCadastro}</td>
                   <td><center><a href="../contaPagarCtrl.do?id=${contaapagar.id}&action=pagar"><img src="../images/sim.png"/></a></center></td>
               </tr>
              </c:if>
           </c:forEach>
           
           <tr>
               <td width="50%">Sub-total: </td> <td width="50%"></td>
           </tr>