Primefaces selectCheckboxMenu how to get the last checked item
<p>I am using selectCheckboxMenu from primefaces, but i need to know which item was checked here is my code: </p>

<pre><code>&lt;p:selectCheckboxMenu
                            label=""
                            id="cboBiblioteca" 
                            filter="true" filterMatchMode="contains"
                            required="false"
                            widgetVar="cboBiblioteca"
                            value="#{documentalBean.sbiblioteca}"
                            style="width:20px"&gt;
                            &lt;p:ajax event="change" listener="#{documentalBean.checkBiblioteca()}"/&gt;
                            &lt;f:selectItems value="#{bibliotecaBean.bibliotecas}" var="biblioteca"  itemLabel="#{biblioteca.NOMBRE_BIBLIOTECA.toLowerCase()}" itemValue="#{biblioteca.ID_BIBLIOTECA_MEDIADOR}"/&gt;
                        &lt;/p:selectCheckboxMenu&gt;
</code></pre>

<p>my "sbiblioteca" array is a String array, when i whatch it on the debugger i cant get the last checked, because they arent added to the last they are added according to their position in the list.</p>