Object IO classes in Java

In Java we can store objects as a byte stream and store it in files or send it over a network. The process of converting an object to a byte stream is serialization and the reverse process of converting a byte stream to an object is called deserialization.
 

In Java programs, we can achieve serialization and deserialization by using the object I/O classes: ObjectOutputStream and ObjectInputStream respectively. These classes are a part of java.io package. The base class for both these classes is InputStream.

ObjectOutputStream class

The ObjectOuputStream class serializes an object into byte stream to store in a file or to send it through a network. Some of the often-used methods in this class are described in the below table:

Following Java program uses ObjectOutputStream class for writing an object to a file. We will also use Serializable interface which allows an object to be serialized.

import java.io.*;
class Student implements Serializable
{
	int id;
	String name;
	Student(int id, String name)
	{
		this.id = id;
		this.name = name;
	}
	public String toString()
	{
		return id + " - " + name;
	}
}
public class Serialization
{
	public static void main(String [] args) throws Exception
	{
		Student s = new Student(1, "Teja");
		ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("students.dat"));
		oos.writeObject(s);
	}
}

The output for the above program is, details of the student are stored in the file students.dat.

ObjectInputStream class

The ObjectInputStream class deserializes a byte stream from a file into object or primitive type data. Some of the often-used methods in this class are described in the below table:

Following Java program uses ObjectInputStream class for reading a byte stream from a file and converting it into an object.

import java.io.*;
public class DeSerialization
{
	public static void main(String [] args) throws Exception
	{
		ObjectInputStream ois = new ObjectInputStream(new FileInputStream("students.dat"));
		Student s = (Student) ois.readObject();
		System.out.println(s);
	}
}

Output for the above program is:

1 – Teja

For more information, visit the following links:

• Java I/O Object Streams
• Package java.io

Suryateja Pericherla

Suryateja Pericherla, at present is a Research Scholar (full-time Ph.D.) in the Dept. of Computer Science & Systems Engineering at Andhra University, Visakhapatnam. Previously worked as an Associate Professor in the Dept. of CSE at Vishnu Institute of Technology, India.

He has 11+ years of teaching experience and is an individual researcher whose research interests are Cloud Computing, Internet of Things, Computer Security, Network Security and Blockchain.

He is a member of professional societies like IEEE, ACM, CSI and ISCA. He published several research papers which are indexed by SCIE, WoS, Scopus, Springer and others.