Java Identity Interface

The identity interface is an interface that does not have any methods and properties, and the identity interface does not have any semantic requirements for the implementation class.
Only indicates that its implementation class belongs to a specific type. It's very similar to the concept of tag in Web 2.0
, which Java uses to identify a class of objects. There are two main uses: first, by the interface to identify the same type of
class, this class itself may not have the same method as the advice interface, and second, by identifying the interface
Make the program or JVM take some special processing, such as Java. Serializable it tells the JVM that objects can be serialized.

Java Identity Interface