java ObjectOutputStream

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

class Employee {
    private String name;

    Employee(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return name;
    }
}

class SerEmployee extends Employee implements Serializable {
    SerEmployee(String name) {
        super(name);
    }
}

public class SerializationDemo {
    public static void main(String[] args) {
        ObjectOutputStream oos = null;
        ObjectInputStream ois = null;
        try {
            oos = new ObjectOutputStream(new FileOutputStream("employee.dat"));
            SerEmployee se = new SerEmployee("John Doe");
            System.out.println(se);
            oos.writeObject(se);
            oos.close();
            oos = null;
            System.out.println("se object written to file");
            ois = new ObjectInputStream(new FileInputStream("employee.dat"));
            se = (SerEmployee) ois.readObject();
            System.out.println("se object read from file");
            System.out.println(se);
        } catch (ClassNotFoundException cnfe) {
            cnfe.printStackTrace();
        }

        catch (IOException ioe) {
            ioe.printStackTrace();
        } finally {
            if (oos != null)
                try {
                    oos.close();
                } catch (IOException ioe) {
                    assert false; // shouldn‘t happen in this context
                }
            if (ois != null)
                try {
                    ois.close();
                } catch (IOException ioe) {
                    assert false; // shouldn‘t happen in this context
                }
        }
    }
}