Java OCA OCP Practice Question 2464

Question

Given the following code to read and write instances of MyClass, which definition of class MyClass will persist only its variable model? 

class ReadWriteObjects {
    public void write(MyClass ph, String fileName) throws Exception {
        ObjectOutputStream oos = new ObjectOutputStream(
                                   new FileOutputStream(fileName));
        oos.writeObject(ph);//from   w  ww.j  av a2  s .  c o  m
        oos.flush();
        oos.close();
    }
    public MyClass read(String fileName) throws Exception {
        ObjectInputStream ois = new ObjectInputStream(
                                   new FileInputStream(fileName));
        MyClass ph = (MyClass)ois.readObject();
        ois.close();
        return ph;
    }
}

a  class MyClass implements Serializable {
       int sessionId;
       String model = "abc";
   }//from  w w  w . ja v a 2s  .  c  om

b  class MyClass {
       transient int sessionId;
       String model = "abc";
   }

c  class MyClass implements Persistable {
       transient int sessionId;
       String model = "abc";
   }

d  class MyClass implements Serializable {
       transient int sessionId;
       String model = "abc";
   }



d

Note

To persist instances of a class, the class must implement the Serializable interface.

Serializable is a marker interface; it doesn't define any methods.

Also, to prevent a field from persisting, define it as a transient variable.

Option (a) doesn't mark the field sessionId as transient.

Option (b) doesn't implement either Serializable or Externalizable.

Option (c) implements the Persistable interface, which doesn't exist.




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