What is the use of marker interfaces in Java?


An interface with no methods in it is referred to as a tagging interface. There are two basic design purposes of tagging interfaces -

Creates a common parent 

As with the EventListener interface, which is extended by dozens of other interfaces in the Java API, you can use a tagging interface to create a common parent among a group of interfaces. For example, when an interface extends EventListener, the JVM knows that this particular interface is going to be used in an event delegation scenario.


Adds a data type to a class

This situation is where the term, tagging comes from. A class that implements a tagging interface does not need to define any methods (since the interface does not have any), but the class becomes an interface type through polymorphism.

Updated on: 30-Jul-2019

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