Custom serialization

import java.io.*;
import java.util.Base64;

public class User implements Serializable {
    String userName;
    transient String password;

    public User(String userName, String password) {
        this.userName = userName;
        this.password = password;
    }

    private void writeObject(ObjectOutputStream oos) throws Exception {
        oos.defaultWriteObject();
        String encryptPassword = encrypt(password);
        oos.writeObject(encryptPassword);
    }

    private void readObject(ObjectInputStream ois) throws Exception {
        ois.defaultReadObject();
        password = decrypt((String) ois.readObject()) + " <- Decrypted password";
    }

    private String encrypt(String password) {
        return Base64.getEncoder().encodeToString(password.getBytes());
    }

    private String decrypt(String encodedString) {
        return new String(Base64.getDecoder().decode(encodedString));
    }

    @Override
    public String toString() {
        return String.format("Name: %s, Pass: %s", userName, password);
    }
}

class UserMain {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        User newUser = new User("Bob", "1qaS3d+67");
        System.out.println("Before serialization " + newUser); // Before serialization Name: Bob, Pass: 1qaS3d+67
        serializeUser(newUser, "new_user_file");

        User oldUser = deserializeUser("new_user_file");
        System.out.println("After serialization " + oldUser); // After serialization Name: Bob, Pass: 1qaS3d+67 <- Decrypted password
    }

    public static User deserializeUser(String filename) throws IOException {
        User deserializedUser = null;
        try (FileInputStream fileIn = new FileInputStream(filename);
            ObjectInputStream ois = new ObjectInputStream(fileIn)) {

            deserializedUser = (User) ois.readObject();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return deserializedUser;
    }

    public static void serializeUser(User user, String filename) throws IOException {
        try (FileOutputStream fileOut = new FileOutputStream(filename);
             ObjectOutputStream oos = new ObjectOutputStream(fileOut)) {

            oos.writeObject(user);
        }
    }
}