code: @Nullable
    private static Class <?> _getUsableClass (@Nullable final Class <?> aClass)
    {
      final Class <?> aPrimitiveWrapperType = ClassHelper.getPrimitiveWrapperClass (aClass);
      return aPrimitiveWrapperType != null ? aPrimitiveWrapperType : aClass;
    }
docs: Get the class to use. In case the passed class is a primitive type, the
  corresponding wrapper class is used.
  
  @param aClass
  The class to check. Can be <code>null</code> but should not be
  <code>null</code>.
  @return <code>null</code> if the parameter is <code>null</code>.