OCPJP sample question wrong on Oracles website

[Gordon Keenan]

Hi,
I am sitting the OCPJP exam this week and I just came across this question in Oracle's list of sample questions for the exam.

import java.io.*;
 public class Network {
   public static void main(String[] args) {
     Traveler t = new Traveler();
     t.x1 = 7; t.x2 = 7; t.x3 = 7;
     // serialize t then deserialize t
     System.out.println(t.x1 + " " + t.x2 + " " + t.x3);
   }
 }
 class Traveler implements Serializable {
   static int x1 = 0;
   volatile int x2 = 0;
   transient int x3 = 0;
 }

If, on line 7, t is successfully serialized and then deserialized, what is the result?

The answer they give is "0 7 0" as correct, stating correctly that static or transient variables are not serialized.

However x1 should still be 7, the same as it is set two lines above as it is static.

So the answer should be 7 7 0.

This does not inspire me with confidence for the exam

The question can be found on the link below, labeled objective 3.3

// You might need to select your region
http://education.oracle.com/pls/web_prod-plq-dad/db_pages.getpage?page_id=303&p_certName=SQ1Z0-851

[Boris Mechkov]

Gordon Keenan wrote:Hi,
I am sitting the OCPJP exam this week and I just came across this question in Oracle's list of sample questions for the exam.

import java.io.*;
 public class Network {
   public static void main(String[] args) {
     Traveler t = new Traveler();
     t.x1 = 7; t.x2 = 7; t.x3 = 7;
     // serialize t then deserialize t
     System.out.println(t.x1 + " " + t.x2 + " " + t.x3);
   }
 }
 class Traveler implements Serializable {
   static int x1 = 0;
   volatile int x2 = 0;
   transient int x3 = 0;
 }

If, on line 7, t is successfully serialized and then deserialized, what is the result?

The answer they give is "0 7 0" as correct, stating correctly that static or transient variables are not serialized.

However x1 should still be 7, the same as it is set two lines above as it is static.

So the answer should be 7 7 0.

This does not inspire me with confidence for the exam

The question can be found on the link below, labeled objective 3.3

// You might need to select your region
http://education.oracle.com/pls/web_prod-plq-dad/db_pages.getpage?page_id=303&p_certName=SQ1Z0-851

If this is indeed the answer they give you - it is wrong. It should be 7 7 0 as you pointed out. I should not worry about it too much. Just follow the principles and you will be fine.

[ai dan]

Has Serialization not been removed?

[Boris Mechkov]

ai dan wrote:Has Serialization not been removed?

It has, so i was surprised when you mentioned this. But, serialization is not that hard to grasp so i would learn it anyway.
Good luck!

[Gordon Keenan]

ai dan wrote:Has Serialization not been removed?

Why would serialization be one of the sample questions if it has been removed, is it another oracle mistake?

Most of the material I have read said has said the topics are identical for the SCJP and OCPJP.

[Gordon Keenan]

Just as a follow up I found the same question on the mock exam from Pearson Vue and they also have the answer wrong.

I just hope it doesn't come up as I will not be sure what to select

[srilatha latha]

Found this in one of java wesites.As per the above explanation, static variable also would not have got the original value after serialization.
I didnot try executing though!
-----------------------------
What are Transient and Volatile Modifiers

A transient variable is a variable that may not be serialized i.e. the value of the variable can’t be written to the stream in a Serializable class. If you don't want some field to be serialized, you can mark that field transient or static. In such a case when the class is retrieved from the ObjectStream the value of the variable is null.

Volatile modifier applies to variables only and it tells the compiler that the variable modified by volatile can be changed unexpectedly by other parts of the program.

[A Phatak]

You are wrong, Oracle's answer is correct. The Answer will be 070, because, serialization will not consider static (x1) and transient(x2). They generally consider that the program will be deserialized at a later time or that it will be deserialized on client. In this paticular case, you are setting static int to 7, and if-and-only-if you serialize and deserialize immediately then you will get x1 to be 7

When you deserialize Traveler, you will do something like this:

ObjectInputStream ois = new ObjectInputStream(new FileInputStream("name_of_serialized_traveler.ser"));
Traveler t_xyz = (Traveler)ois.readObject();
System.out.println(t_xyz.x1 + " " t_xyz.x2 + " " + t_xyz.x3); // clearly values will be 0 7 0

[Dan Drillich]

I agree with Anang about 070. I don't see how the static x1 can retain its value of 7 through the process of serialization and then deserializtion.

Regards,
Dan

[Keith Rainey]

I purchased the practice exams available directly from Oracle. I, too, found a couple of questions where I disagreed with their 'correct' answer. As I was studying, my general procedure was to take the code in the questions I missed and actually plug it in to Eclipse and see who was right.

A different concern with the practice tests from Oracle was that I saw duplicate questions 5 or 6 times in a question that had only 60 questions.

Best of luck on the exam!