NotSerializableException in Java with Examples

// Java Program to Illustrate NotSerializableException
// Where Exception Is Thrown

// Importing required classes
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;

// Class 1
// Helper class
class Employee {

    // Member variables
    private String id;

    // Member methods

    // Method 1
    // To get ID of an employee
    public String getId() { return id; }

    // Method 1
    // To set ID of an employee
    public void setId(String id)
    {

        // this keyword refers to current object itself
        this.id = id;
    }
}

// Class 2
// Main Class
public class GFG {

    // Main driver method
    public static void main(String[] args)
        throws IOException
    {

        // Create FileOutputStream class object  to
        // create a file
        FileOutputStream out
            = new FileOutputStream("employee.dat");

        // Similarly creating ObjectOutputStream class
        // object
        ObjectOutputStream outputStream
            = new ObjectOutputStream(out);

        // Creating objects of class 1
        Employee obj = new Employee();

        // Assifning ID to an employee
        obj.setId("001");

        // Writing objects to stream
        outputStream.writeObject(obj);

        // Good practice is always to
        // Close the stream using close() method
        outputStream.close();
    }
}

// Java Program to Illustrate NotSerializableException
// where No Exception is Thrown Using Serializable interface

// Importing input output class
import java.io.Serializable;

// By implementing Serializable interface
// we are allowing Student object to
// be stored in TestFile.txt

// Class 1
// Helper class extending to Serializable interface
class Student implements Serializable {

    // Member variables of this class
    int id;
    String name;

    // Constructor of this class
    public Student(int id, String name)
    {
        this.id = id;
        this.name = name;
    }
}

// Class 2
// Main class
class Persist {

    // Main driver method
    public static void main(String args[])
    {

        // try block to check for exceptions
        try {

            // Creating the object
            Student s1 = new Student(007, "Test");

            // Creating stream and writing the object
            FileOutputStream fout
                = new FileOutputStream("TestFile.txt");
            ObjectOutputStream out
                = new ObjectOutputStream(fout);

            out.writeObject(s1);
            out.flush();

            // Closing the stream to free up memory space
            // using close() method
            out.close();

            // Display command to shown proper execution of
            // a program
            System.out.println(
                "Object stored successfully");
        }

        // Catch block to handle the exceptions
        catch (Exception e) {

            // Print and display the exception on the
            // console
            System.out.println(e);
        }
    }
}