Last Updated : 02 Jun, 2025
In Java, serialization plays a very important role it's something that we use a lot in our real life, even if we do not always notice it. Serialization helps us to save the current state of an object so that we can use it further and share complex data between different systems. In this article, we will discuss a lot more about serialization and deserialization in Java for better understanding and clarity.
What is Serialization and Deserialization?Serialization is a mechanism of converting the state of an object into a byte stream.
Important Points of Serialisation:
Deserialization is the reverse process where the byte stream is used to recreate the actual Java object in memory. This mechanism is used to persist the object.
Important Points of Deserialization:
The image below demonstrates the process of serialization and deserialization.
Serialization Process: The byte stream created is platform independent. So, the object serialized on one platform can be deserialized on a different platform. To make a Java object serializable we implement the java.io.Serializable interface. The ObjectOutputStream class contains writeObject() method for serializing an Object.
public final void writeObject(Object obj)
throws IOException
Advantages of Serialization:
Deserialization Process: The ObjectInputStream class contains readObject() method for deserializing an object.
public final Object readObject()
throws IOException,
ClassNotFoundException
Advantages of Deserialization:
Serializable Interface and Marker Interfaces
Only the objects of those classes can be serialized which are implementing java.io.Serializable interface. Serializable is a marker interface (has no data member and method). It is used to "mark" java classes so that objects of these classes may get certain capability. Other examples of marker interfaces are:- Cloneable and Remote.
Points to remember while using Serialization:
Example:
SerialVersionUIDclass A implements Serializable{
// B also implements Serializable
// interface.
B ob=new B();
}
The Serialization runtime associates a version number with each Serializable class called a SerialVersionUID, which is used during Deserialization to verify that sender and receiver of a serialized object have loaded classes for that object which are compatible with respect to serialization. If the receiver has loaded a class for the object that has different UID than that of corresponding sender's class, the Deserialization will result in an InvalidClassException.
Syntax:
private static final long serialVersionUID = 3L;
A Serializable class can declare its own UID explicitly by declaring a field name. It must be static, final and of type long. i.e- ANY-ACCESS-MODIFIER static final long serialVersionUID=42L; If a serializable class doesn't explicitly declare a serialVersionUID, then the serialization runtime will calculate a default one for that class based on various aspects of class, as described in Java Object Serialization Specification.
However it is strongly recommended that all serializable classes explicitly declare serialVersionUID value, since its computation is highly sensitive to class details that may vary depending on compiler implementations, any change in class or using different id may affect the serialized data. It is also recommended to use private modifier for UID since it is not useful as inherited member. serialver The serialver is a tool that comes with JDK. It is used to get serialVersionUID number for Java classes.
Example of Getting SerialVersionUID using SerialverWe can run the following command to get serialVersionUID serialver [-classpath classpath] [-show] [classname...]
Example: Serialization and Deserialization of a Java Object.
Java
import java.io.*;
class Demo implements Serializable {
public int a;
public String b;
public Demo(int a, String b) {
this.a = a;
this.b = b;
}
}
public class Geeks {
public static void main(String[] args) {
Demo object = new Demo(1, "geeksforgeeks");
String filename = "file.ser";
// Serialization
try {
FileOutputStream file = new FileOutputStream(filename);
ObjectOutputStream out = new ObjectOutputStream(file);
out.writeObject(object);
out.close();
file.close();
System.out.println("Object has been serialized");
} catch (IOException ex) {
System.out.println("IOException is caught");
}
Demo object1 = null;
// Deserialization
try {
FileInputStream file = new FileInputStream(filename);
ObjectInputStream in = new ObjectInputStream(file);
object1 = (Demo) in.readObject();
in.close();
file.close();
System.out.println("Object has been deserialized");
System.out.println("a = " + object1.a);
System.out.println("b = " + object1.b);
} catch (IOException ex) {
System.out.println("IOException is caught");
} catch (ClassNotFoundException ex) {
System.out.println("ClassNotFoundException is caught");
}
}
}
Output:
Example: Serialization with Transient and Static Fields.
Java
import java.io.*;
class Emp implements Serializable {
private static final long serialVersionUID = 129348938L;
transient int a;
static int b;
String name;
int age;
public Emp(String name, int age, int a, int b) {
this.name = name;
this.age = age;
this.a = a;
this.b = b;
}
}
public class Geeks{
public static void printData(Emp object1) {
System.out.println("name = " + object1.name);
System.out.println("age = " + object1.age);
System.out.println("a = " + object1.a);
System.out.println("b = " + object1.b);
}
public static void main(String[] args) {
Emp object = new Emp("ab", 20, 2, 1000);
String filename = "shubham.txt";
// Serialization
try {
// Saving of object in a file
FileOutputStream file = new FileOutputStream(filename);
ObjectOutputStream out = new ObjectOutputStream(file);
out.writeObject(object);
out.close();
file.close();
System.out.println("Object has been serialized\nData before Deserialization.");
printData(object);
// Change static variable b
object.b = 2000;
} catch (IOException ex) {
System.out.println("IOException is caught");
}
object = null;
// Deserialization
try {
// Reading the object from a file
FileInputStream file = new FileInputStream(filename);
ObjectInputStream in = new ObjectInputStream(file);
object = (Emp) in.readObject();
in.close();
file.close();
System.out.println("Object has been deserialized\nData after Deserialization.");
printData(object);
} catch (IOException ex) {
System.out.println("IOException is caught");
} catch (ClassNotFoundException ex) {
System.out.println("ClassNotFoundException is caught");
}
}
}
Object has been serialized Data before Deserialization. name = ab age = 20 a = 2 b = 1000 Object has been deserialized Data after Deserialization. name = ab age = 20 a = 0 b = 2000
Explanation In the above code while deserializing the object the values of a and b has changed. The reason being a was marked as transient and b was static.
The main difference between Transient and Final is listed below:
Example:
final int x= 10;
int y = 20;
System.out.println(x);// compiler will replace this as System.out.println(10)->10
because x is final.
System.out.println(y);//20
Example: Demonstration of transient and final behaviour together while serialization.
Java
// Java program for final with transient
import java.io.*;
class Dog implements Serializable{
int i=10;
transient final int j=20;
}
class Geeks
{
public static void main (String[] args)throws
IOException, ClassNotFoundException
{
Dog d1=new Dog();
//Serialization started
System.out.println("serialization started");
FileOutputStream fos= new FileOutputStream("abc.ser");
ObjectOutputStream oos=new ObjectOutputStream(fos);
oos.writeObject(d1);
System.out.println("Serialization ended");
//Deserialization started
System.out.println("Deserialization started");
FileInputStream fis=new FileInputStream("abc.ser");
ObjectInputStream ois=new ObjectInputStream(fis);
Dog d2=(Dog) ois.readObject();
System.out.println("Deserialization ended");
System.out.println("Dog object data");
//final result
System.out.println(d2.i+"\t" +d2.j);
}
}
serialization started Serialization ended Deserialization started Deserialization ended Dog object data 10 20Serialization vs Deserialization in Java
The main difference between serialization and deserialization is:
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