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In Java interviews, one of the most common topics you’ll encounter is object persistence —how Java objects are saved, transferred, and reconstructed. This is where concepts like Serialization , Deserialization , and Externalization come into play. These aren’t just theoretical ideas; they are crucial in distributed systems, caching, session management, and inter-process communication . Let’s explore these concepts step by step, highlight their differences, and discuss real-world use cases. 1. What is Serialization in Java? Serialization is the process of converting a Java object into a byte stream so that it can be stored in a file, transmitted over a network, or persisted in a database. How it works: The class must implement the Serializable interface (marker interface). Use ObjectOutputStream.writeObject() to serialize an object. Non-transient, non-static fields are serialized; transient fields are skipped. ...

In Java, a Marker Interface is an interface that does not contain any methods or fields. It serves as a “tag” or “marker” to give special meaning to the classes that implement it. This way, the Java runtime or compiler can identify those classes and provide them with additional capabilities. 🔹 What is a Marker Interface? A marker interface is essentially an empty interface. When a class implements a marker interface, it tells the JVM that the class should be treated in a particular way. // Example of a Marker Interface public interface Serializable { // No methods or fields } public class Student implements Serializable { private int id; private String name; } Here, the Student class implements Serializable . Even though the interface is empty, the JVM knows that objects of Student can be serialized. 🔹 Popular Examples of Marker Interfaces in Java Serializable – Marks classes so their objects...