SelectCheckboxMenu SelectManyCheckbox is used to choose multiple items displayed in an overlay.
Submit
No cities selected
<h:form>
    <h:panelGrid columns="3" cellpadding="5">
        <h:outputLabel for="menu" value="Location:" />
        <p:selectCheckboxMenu id="menu" value="#{checkboxView.selectedCities}" label="Cities" 
                              filter="true" filterMatchMode="startsWith" panelStyle="width:250px">
            <f:selectItems value="#{checkboxView.cities}" />
        </p:selectCheckboxMenu>
        <p:commandLink value="Submit" update="display" />
    </h:panelGrid>

    <p:outputPanel id="display" style="width:250px;padding-left:5px;margin-top:10px">
        <p:dataList value="#{checkboxView.selectedCities}" var="city" emptyMessage="No cities selected">
            #{city}
        </p:dataList>
    </p:outputPanel>
</h:form>
                
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