doubt based on construtor

[sankar kandasamy]

I saw one question in SCJP model question. The question:

import java.io.*;
class Player {
Player() { System.out.print("p"); }
}
class CardPlayer extends Player implements Serializable {
CardPlayer() { System.out.print("c"); }
public static void main(String[] args) {
CardPlayer c1 = new CardPlayer();
try {
FileOutputStream fos = new FileOutputStream("play.txt");
ObjectOutputStream os = new ObjectOutputStream(fos);
os.writeObject(c1);
os.close();
FileInputStream fis = new FileInputStream("play.txt");
ObjectInputStream is = new ObjectInputStream(fis);
CardPlayer c2 = (CardPlayer) is.readObject();
is.close();
} catch (Exception x ) { }
}
}

For this question I guess the answer as
pc
but it gives the answer as:
pcp

I cant understand how this answer comes.
I cant understand when the base class contrutor secone time called
pls help me

[Praveen Seluka]

Hi

Note that superclass player is not serialized while subclass cardplayer is serialized.generally when deserializing the constructor doesnt run.But in this case,as the super class player does not implement serializable,the Objects state would not have been stored during serialization.
So when deserializing the superclass constructor runs,and sets player to its initial state.

Thanks
Praveen SP

[Abhishek khare]

CardPlayer c2 = (CardPlayer) is.readObject();

at this POINT the when you deserealize the Object C2(CardPlayer) is deserealized but however since Player does not implement Serializable its constructor will be called.

change code to


import java.io.*;
class Player implements Serializable {
Player() {
System.out.print("p");
}
}
public class CardPlayer extends Player implements Serializable {
CardPlayer() {
System.out.print("c");
}
public static void main(String[] args) {
CardPlayer c1 = new CardPlayer();
try {
FileOutputStream fos = new FileOutputStream("play.txt");
ObjectOutputStream os = new ObjectOutputStream(fos);
os.writeObject(c1);
os.close();
FileInputStream fis = new FileInputStream("play.txt");
ObjectInputStream is = new ObjectInputStream(fis);
CardPlayer c2 = (CardPlayer) is.readObject();
is.close();
} catch (Exception x ) {

}
}
}
and you wil get O/P as "pc"

Hope it helps

[Yogvinder Singh Ghotra]

Moreover, i think only the default no arg constructor is called during de-serialization.

[sankar kandasamy]

I got it . Thanks for all