Using empty interfaces as markers to distinguish special treated objects.

Use the Marker Interface pattern when

• you want to identify the special objects from normal objects (to treat them differently)
• you want to mark that some object is available for certain sort of operations

• javase.8.docs.api.java.io.Serializable
• javase.8.docs.api.java.lang.Cloneable

• Effective Java 2nd Edition by Joshua Bloch