// Java program to illustrate loss of information
// because of transient keyword.
import java.io.*;
  
class GfgAccount implements Serializable {
  
    String username = "gfg_admin";
  
    transient String pwd = "geeks";
  
}
  
class CustomizedSerializationDemo {
    public static void main(String[] args) throws Exception
    {
        GfgAccount gfg_g1 = new GfgAccount();
  
        System.out.println("Username : " + gfg_g1.username + 
                                 "    Password : " + gfg_g1.pwd);
  
        FileOutputStream fos = new FileOutputStream("abc.ser");
  
        ObjectOutputStream oos = new ObjectOutputStream(fos);
  
        // writeObject() method present in GfgAccount class
        // will be automatically called by jvm
        oos.writeObject(gfg_g1);
  
        FileInputStream fis = new FileInputStream("abc.ser");
  
        ObjectInputStream ois = new ObjectInputStream(fis);
  
        // readObject() method present GfgAccount class
        // will be automatically called by jvm
        GfgAccount gfg_g2 = (GfgAccount)ois.readObject();
  
        System.out.println("Username : " + gfg_g2.username + 
                               "      Password : " + gfg_g2.pwd);
    }
}

Username : gfg_admin    Password : geeks
Username : gfg_admin    Password : null

// Java program to illustrate customized serialization
import java.io.*;
  
class GfgAccount implements Serializable {
  
    String username = "gfg_admin";
  
    transient String pwd = "geeks";
  
    // Performing customized serialization using the below two methods:
    // this method is executed by jvm when writeObject() on
    // Account object reference in main method is
    // executed by jvm.
    private void writeObject(ObjectOutputStream oos) throws Exception
    {
        // to perform default serialization of Account object.
        oos.defaultWriteObject();
  
        // epwd (encrypted password)
        String epwd = "123" + pwd;
  
        // writing encrypted password to the file
        oos.writeObject(epwd);
    }
  
    // this method is executed by jvm when readObject() on
    // Account object reference in main method is executed by jvm.
    private void readObject(ObjectInputStream ois) throws Exception
    {
        // performing default deserialization of Account object
        ois.defaultReadObject();
  
        // deserializing the encrypted password from the file
        String epwd = (String)ois.readObject();
  
        // decrypting it and saving it to the original password
        // string starting from 3rd  index till the last index
        pwd = epwd.substring(3);
    }
}
  
class CustomizedSerializationDemo {
    public static void main(String[] args) throws Exception
    {
        GfgAccount gfg_g1 = new GfgAccount();
  
        System.out.println("Username :" + gfg_g1.username +
                           "       Password :" + gfg_g1.pwd);
  
        FileOutputStream fos = new FileOutputStream("abc.ser");
  
        ObjectOutputStream oos = new ObjectOutputStream(fos);
  
        // writeObject() method on Account class will
        // be automatically called by jvm
        oos.writeObject(gfg_g1);
  
        FileInputStream fis = new FileInputStream("abc.ser");
  
        ObjectInputStream ois = new ObjectInputStream(fis);
  
        GfgAccount gfg_g2 = (GfgAccount)ois.readObject();
  
        System.out.println("Username :" + gfg_g2.username + 
                             "       Password :" + gfg_g2.pwd);
    }
}

Username :gfg_admin    Password :geeks
Username :gfg_admin    Password :geeks