import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * Created by Alexis on 28-Apr-17. * With Marker interface idea is to make empty interface and extend it. * Basically it is just to identify the special objects from normal objects. * Like in case of serialization , objects that need to be serialized must implement serializable interface * (it is empty interface) and down the line writeObject() method must be checking * if it is a instance of serializable or not. *
* Marker interface vs annotation * Marker interfaces and marker annotations both have their uses, * neither of them is obsolete or always better then the other one. * If you want to define a type that does not have any new methods associated with it, * a marker interface is the way to go. * If you want to mark program elements other than classes and interfaces, * to allow for the possibility of adding more information to the marker in the future, * or to fit the marker into a framework that already makes heavy use of annotation types, * then a marker annotation is the correct choice */ public class App { /** * Program entry point * * @param args command line args */ public static void main(String[] args) { final Logger logger = LoggerFactory.getLogger(App.class); Guard guard = new Guard(); Thief thief = new Thief(); if (guard instanceof Permission) { guard.enter(); } else { logger.info("You have no permission to enter, please leave this area"); } if (thief instanceof Permission) { thief.steal(); } else { thief.doNothing(); } } }