Serialization and deserialization

import java.io.*;

class Book implements Serializable {
    private static final long serialVersionUID = 1L;
    String title;
    int price;
}

public class Main {
    public static void main(String[] args) throws Exception {
        Book b = new Book();
        b.title = "Java Basics";
        b.price = 399;
        try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("book.ser"))) {
            out.writeObject(b);
        }
        try (ObjectInputStream in = new ObjectInputStream(new FileInputStream("book.ser"))) {
            Book copy = (Book) in.readObject();
            System.out.println(copy.title + " Rs " + copy.price);
        }
    }
}

import java.io.*;

class Login implements Serializable {
    private static final long serialVersionUID = 1L;
    String user = "asha";
    transient String password = "secret123";
}

public class Main {
    public static void main(String[] args) throws Exception {
        try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("login.ser"))) {
            out.writeObject(new Login());
        }
        try (ObjectInputStream in = new ObjectInputStream(new FileInputStream("login.ser"))) {
            Login l = (Login) in.readObject();
            System.out.println("user=" + l.user + ", password=" + l.password);
        }
    }
}

import java.io.*;
import java.nio.file.*;

public class Main {
    public static void main(String[] args) throws IOException {
        try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("s.ser"))) {
            out.writeObject("hello");
        }
        byte[] b = Files.readAllBytes(Path.of("s.ser"));
        System.out.printf("%02X %02X %02X %02X (%d bytes)%n", b[0], b[1], b[2], b[3], b.length);
    }
}

import java.io.*;

class Ticket implements Serializable {
    private static final long serialVersionUID = 1L;
    static int made = 0;
    int seat;
    Ticket(int seat) { this.seat = seat; made++; }
}

public class Main {
    public static void main(String[] args) throws Exception {
        try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("t.ser"))) {
            out.writeObject(new Ticket(14));
        }
        try (ObjectInputStream in = new ObjectInputStream(new FileInputStream("t.ser"))) {
            Ticket t = (Ticket) in.readObject();
            System.out.println("seat " + t.seat + ", constructor calls: " + Ticket.made);
        }
    }
}

import java.io.*;

class Config implements Serializable {
    private static final long serialVersionUID = 1L;
    static String theme = "light";
    String user = "meena";
}

public class Main {
    public static void main(String[] args) throws Exception {
        try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("cfg.ser"))) {
            out.writeObject(new Config());
        }
        Config.theme = "dark";
        try (ObjectInputStream in = new ObjectInputStream(new FileInputStream("cfg.ser"))) {
            Config c = (Config) in.readObject();
            System.out.println("user=" + c.user + ", theme=" + Config.theme);
        }
    }
}

import java.io.*;

class Printer {
    String model = "TP-80";
}

class Order implements Serializable {
    private static final long serialVersionUID = 1L;
    int id = 501;
    Printer printer = new Printer();
}

public class Main {
    public static void main(String[] args) throws IOException {
        try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("o.ser"))) {
            out.writeObject(new Order());
        } catch (NotSerializableException e) {
            System.out.println("cannot save: " + e.getMessage() + " is not Serializable");
        }
    }
}

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

class Customer implements Serializable {
    private static final long serialVersionUID = 1L;
    String name, city;
    int points;
    Customer(String n, String c, int p) { name = n; city = c; points = p; }
}

public class Main {
    @SuppressWarnings("unchecked")
    public static void main(String[] args) throws Exception {
        List<Customer> list = new ArrayList<>(List.of(
            new Customer("Asha", "Pune", 120), new Customer("Ravi", "Nagpur", 300), new Customer("Imran", "Pune", 75)));
        try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("customers.ser"))) {
            out.writeObject(list);
        }
        try (ObjectInputStream in = new ObjectInputStream(new FileInputStream("customers.ser"))) {
            List<Customer> loaded = (List<Customer>) in.readObject();
            int total = 0;
            for (Customer c : loaded) total += c.points;
            System.out.println(loaded.size() + " customers, " + total + " points in total");
        }
    }
}

import java.io.*;

class Address implements Serializable {
    private static final long serialVersionUID = 1L;
    String city = "Mumbai";
}

class Employee implements Serializable {
    private static final long serialVersionUID = 1L;
    String name;
    Address office;
    Employee(String n, Address a) { name = n; office = a; }
}

public class Main {
    public static void main(String[] args) throws Exception {
        Address hq = new Address();
        try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("staff.ser"))) {
            out.writeObject(new Employee("Asha", hq));
            out.writeObject(new Employee("Ravi", hq));
        }
        try (ObjectInputStream in = new ObjectInputStream(new FileInputStream("staff.ser"))) {
            Employee a = (Employee) in.readObject();
            Employee r = (Employee) in.readObject();
            System.out.println("same office object? " + (a.office == r.office) + ", city " + r.office.city);
        }
    }
}

import java.io.*;

class Invoice implements Serializable {
    private static final long serialVersionUID = 2026_10L;
    String number;
    double amount;
}

public class Main {
    public static void main(String[] args) {
        ObjectStreamClass desc = ObjectStreamClass.lookup(Invoice.class);
        System.out.println(desc.getName() + " serialVersionUID = " + desc.getSerialVersionUID());
        System.out.println("fields saved: " + desc.getFields().length);
    }
}