Serialization for statics

[Chaitanya Kidambi]

Holla everyone,

This question is from oracle website (sample questions).

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


public class Net {
	public static void main(String[] args) throws Exception {
		Travel t = new Travel();
		t.x=7;
		t.y=7;
		t.z=7;
		ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("abc.txt"));
		oos.writeObject(t);
		oos.flush();
		oos.close();
		ObjectInputStream ois = new ObjectInputStream(new FileInputStream("abc.txt"));
		t = (Travel) ois.readObject();
		System.out.println(t.x + " " + t.y + " " + t.z); 
	}

}
class Travel implements Serializable {
	static int x=0;
	volatile int y=0;
	transient int z=0;
}

output is 7 7 0


but according to the answers given in the website its 0 7 0.
can any one please tell me what is wrong with this code ? i know that static variables cannot be serialized.
you can check the question Here

Thanks a lott

[Andreas Svenkson]

Like you say, statics aren't serialized. However.... This code is launched during one instance of a JVM. You set the static variable to 7, and the reason it prints 7 after deserialization is because it is still 7. But it has nothing to do with the deserialization, it's just that the value hasn't changed since you serialized your object t.

Hope that was clear...

EDIT: As for the answer according to the website, I assume its an error.

// Andreas

[Aashu Mahajan]

Hi, Chaitanya Kidambi

You are right, static variable or class variable has nothing to do with Serialization and Desirialization. I liitle modified your code, see here

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


public class Net {
	public static void main(String[] args) throws Exception {
		Travel t = new Travel();
		t.x=7;
		t.y=7;
		t.z=7;
		ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("abc.txt"));
		oos.writeObject(t);
		oos.flush();
		oos.close();
		t.x = 8;
		t.y = 9;
		t.z = 10;
		ObjectInputStream ois = new ObjectInputStream(new FileInputStream("abc.txt"));
		t = (Travel) ois.readObject();
		System.out.println(t.x + " " + t.y + " " + t.z); 
	}

}
class Travel implements Serializable {
	static int x=0;
	volatile int y=0;
	transient int z=0;
}

Output : 8 7 0

[Muneeswaran Balasubramanian]

hi Aashu,

You are right.You give the crystal clear soluntion.

[Chaitanya Kidambi]

Andreas Svenkson wrote:

EDIT: As for the answer according to the website, I assume its an error.

// Andreas

Hello there, yeah it might be an error. thanks for the reply.

[Chaitanya Kidambi]

Aashu Mahajan wrote:Hi, Chaitanya Kidambi


Output : 8 7 0

Hello Aashu,
thanks for the reply.