code: public static boolean isInterface (@Nullable final Class <?> aClass)
    {
      return aClass != null && Modifier.isInterface (aClass.getModifiers ());
    }
docs: Check if the passed class is an interface or not. Please note that
  annotations are also interfaces!
  
  @param aClass
  The class to check.
  @return <code>true</code> if the class is an interface (or an annotation)