Primefaces Checkboxmenu Default String Modification

User Story:

When ticking 0 to n Objects from a Primefaces Checkboxmenu (also called selectCheckboxMenu), the displayed String

• has to be Object.name if 1 Item is selected.

• has to be every Objects name whoms Object has been selected, seperated by Commas, if more than 1 Item is selected.

• has to be a default value, if nothing is selected.

Question:

What do i need to do in order to set the displayed String dynamically (like this), when for example a selectionchanged event is thrown?

Additional Info

Im using Primefaces in Version 5.2, JSF in Version 2.2 and Omnifaces in Version 1.5