Serialization and deserialization

[Pinki Roy]

I am not clear why the answer is A B A.

Someone please clarify it, please.


public class A {
public A() {
System.out.println("A");
}
}

public class B extends A implements Serializable {
public B() {
System.out.println("B");
}

}

public class Test {

public static void main(String... args) throws Exception {
B b = new B();

ObjectOutputStream save = new ObjectOutputStream(new FileOutputStream("datafile"));
save.writeObject(b);
save.flush();


ObjectInputStream restore = new ObjectInputStream(new FileInputStream("datafile"));
B z = (B) restore.readObject();



}

}

[Astha Sharma]

Whe object is formed in line B b = new B(); construncors of both classes is called. It prints AB.
K&B -

If you are a serializable class, but your superclass is not serializable, then any instance variables you inherit from that superclass will be reset to the values they were given during the original construction of the object. This is because the non-serializable class constructor will run!
thus again constructor of superclass is called and A gets printed.

[Sebanti Sanyal]

Wanted to mention a situation here when the non-serializable superclass does not have a no-arg constructor. De-serialization in that case will throw a run-time exception.

[Mohamed Sanaulla]

Please UseCodeTags to post your code.

[Helen Ma]

According to the practice exam book, it says object serialization and deserialization are removed from the exam objective for OCPJP 6.0 . But it is good to learn about it though.