What is the use of marker interfaces in Java?

Solution 1:

Joshua Bloch: Effective Java 2nd Edition, p 179

Item 37: Use marker interfaces to define types

... You may hear it said that marker annotations (Item 35) make marker interfaces obsolete. This assertion is incorrect. Marker interfaces have two advantages over marker annotations. First and foremost, marker interfaces define a type that is implemented by instances of the marked class; marker annotations do not. The existence of this type allows you to catch errors at compile time that you couldn’t catch until runtime if you used a marker annotation....

Personally I think I'll bow to Joshua's superior knowledge on this subject.

Solution 2:

In earlier versions of Java, Marker Interfaces were the only way to declare metadata about a class. For example, the Serializable Marker Interface lets the author of a class say that their class will behave correctly when serialized and deserialized.

In modern Java, marker interfaces have no place. They can be completely replaced by Annotations, which allow for a very flexible metadata capability. If you have information about a class, and that information never changes, then annotations are a very useful way to represent it.