/*The only purpose is to mark a declaration.
These annotations contain no members and do not consist any data.
Thus, its presence as an annotation is sufficient.
Since, marker interface contains no members, simply determining whether it is present or absent is sufficient.
@Override is an example of Marker Annotation.
Example: - */
@TestAnnotation()

A Marker Interface in Java is an interface that doesn't declare any required methods, but its presence alone indicates something about the implementing class to both the compiler and the runtime environment. Marker interfaces are used to provide metadata or behavioral information to classes that implement them.
Marker interfaces are also sometimes referred to as "tag" interfaces.
One well-known example of a marker interface in Java is the Serializable interface. When a class implements the Serializable interface, it indicates to Java's serialization mechanism that objects of that class can be serialized (converted to a stream of bytes) and deserialized (reconstructed from the stream of bytes).
Here's an example of the Serializable marker interface:
import java.io.Serializable;
public class Student implements Serializable { private String name; private int age; // Constructors, getters, setters, etc.
}
public interface Printable { // No methods declared
}
public class Book implements Printable { // Class implementation
}
public class Document implements Printable { // Class implementation
}

// An empty interface that has no methods or constants inside it, is known as a marker interface.
// if the object is tagged with Cloneable then JVM knows that it has to call Object.clone() for this object.
// Thus, marker interface ‘Cloneable’ is the indication to JVM for performing cloning.
public interface cloneable {
}
// You can use the marker interface in Java for commenting as well.
// For example – if you mark a class at @ThreadSafe – it will better communicate to fellow developers that the class is designed to be a thread-safe class and could be used that way