marker doesnt have methods but they accomplish the task if a class implements the marker interface,Any interface without a method acts like a marker. They just tell the compiler that the objects of the class implementing the marker interface has to be treated differently. Example Its used in the process of serialization. To send an object over network or if the state of the object has to be persisted to a flat file or a database. Deep cloning can be achieved through serialization. This may be fast to code but will have performance.