Java: Serialization and Deserialization

Serialization is a mechanism to convert the state of the object into a byte stream and deserialization is a reverse mechanism where the byte stream is used to recreate the actual object.

The mechanism is used to persist the object state

The byte stream which is created is a platform independent so that it can be deserialized in any platform.

Note : only those objects can be serialized which are implementation java.io.serializable interface, this interface is a marker interface and has no members and methods.

Note 2: Static data member and transient members are not serialized

// Java code for serialization and deserialization 
// of a Java object
import java.io.*;

class Demo implements java.io.Serializable
{
    public int a;
    public String b;

    // Default constructor
    public Demo(int a, String b)
    {
        this.a = a;
        this.b = b;
    }

}

class Test
{
    public static void main(String[] args)
    {   
        Demo object = new Demo(1, "geeksforgeeks");
        String filename = "file.ser";

        // Serialization 
        try
        {   
            //Saving of object in a file
            FileOutputStream file = new FileOutputStream(filename);
            ObjectOutputStream out = new ObjectOutputStream(file);

            // Method for serialization of object
            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
        {   
            // Reading the object from a file
            FileInputStream file = new FileInputStream(filename);
            ObjectInputStream in = new ObjectInputStream(file);

            // Method for deserialization of object
            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 :

Object has been serialized
Object has been deserialized 
a = 1
b = geeksforgeeks