Marker Interfaces

An interface without fields or methods is called a marker interface. They are used to hint the compiler or the JVM.

public class Message implements Serializable {}

The Serializable is a marker interface. The above will allow the Message class to be serialized.

Serialization is the process of converting an object into a stream of bytes or store the object or to transmit it to memory, database, or a file.

Its main purpose is to save the state of an object in order or be able to recreate it when needed. The reverse process is called deserialization.