returning a Void object

The Void class is an uninstantiable placeholder class to hold a reference to the Class object representing the Java keyword void.

So any of the following would suffice:

• parameterizing with Object and returning new Object() or null
• parameterizing with Void and returning null
• parameterizing with a NullObject of yours

You can’t make this method void, and anything else returns something. Since that something is ignored, you can return anything.