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Question about Serialization

Apratim Khandalkar
Ranch Hand

Joined: Jan 09, 2006
Posts: 34
Hi All,

Following is the mock question at the end of chapter 6 from K & B Book.


import java.io.*;
public class TestSer {
public static void main(String[] args) {
SpecialSerial s = new SpecialSerial();
try {
ObjectOutputStream os = new ObjectOutputStream(
new FileOutputStream("myFile"));
os.writeObject(s); os.close();
System.out.print(++s.z + " ");
ObjectInputStream is = new ObjectInputStream(
new FileInputStream("myFile"));
SpecialSerial s2 = (SpecialSerial)is.readObject();
is.close();
System.out.println(s2.y + " " + s2.z);
} catch (Exception x) {System.out.println("exc"); }
}
}
class SpecialSerial implements Serializable {
transient int y = 7;
static int z = 9;
}



Which are true? (Choose all that apply.)
A. Compilation fails.
B. The output is 10 0 9
C. The output is 10 0 10
D. The output is 10 7 9
E. The output is 10 7 10
F. In order to alter the standard deserialization process you would override the readObject()
method in SpecialSerial.
G. In order to alter the standard deserialization process you would override the defaultReadObject() method in SpecialSerial

Answer is
C and F are correct. C is correct because static and transient variables are not serialized when an object is serialized. F is a valid statement.

I am confused if C is correct then why F is also correct please help
Henry Wong
author
Sheriff

Joined: Sep 28, 2004
Posts: 18752
    
  40

Answer is
C and F are correct. C is correct because static and transient variables are not serialized when an object is serialized. F is a valid statement.

I am confused if C is correct then why F is also correct please help


How about wording it like this? ... The output is 10 0 10, because in the standard serialization process, static and transient variables are not serialized when an object is serialized. However, if you would like to alter the standard serialization process to serialize static and transient variables, you would override the readObject() method in the SpecialSerial class.

Does this statement include both C and F, and still make sense?

Henry


Books: Java Threads, 3rd Edition, Jini in a Nutshell, and Java Gems (contributor)
Shivey Upadhyay
Greenhorn

Joined: Oct 05, 2007
Posts: 29
Henry, you said perfectly correct, Serialization is not for statics! and whenever, deserialization is done, transients are given their default values not initialized values.
In order to write and read something extra during serialization, to save it with object's state and retreive it! we override writeObject(ObjectOutputStream os) and readObject(ObjectInputStream ois), and we invoke defaultWriteObject() and defaultReadObject() to tell the JVM to do normal serialization process. But what happens if i do not invoke these methods, and directly write an int say writeInt(i) and then readInt(i).
Actually, i have my exam next weekend, and i would really appriciate the answer.


Thanks,
Shivey
SCJP, SCWCD, and Aspiring SCDJWS
 
I agree. Here's the link: http://aspose.com/file-tools
 
subject: Question about Serialization