serialization question

[William Yan]

Hi ranchers,
I saw this in a K&B exam.

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) {
}
}
}

The output is 'pcp'.
I don't know why the 2nd 'p' is printed.
Thankyou.

[Bing Qiao]

The base class doesn't implement Serializable Interface which means the constructor of the base class will be called during the deserialization of the subclass.

[William Yan]

^O^
Got it.
Thanks a lot.