Getting ready

A private interface method must have an implementation (a body with a code). A private interface method not used by other methods of the same interface does not make sense. The purpose of a private method is to contain functionality that is common between two or more methods with a body in the same interface or to isolate a section of code in a separate method for better structure and readability. A private interface method cannot be overridden—not by a method of any other interface, nor by a method in a class that implements the interface.  

A non-static private interface method can only be accessed by non-static methods of the same interface. A static private interface method can be accessed by non-static and static methods of the same interface.