SCJP : Serializable Mock Exam Practice Questions

Questions no -1 
What is the output for the below code ?

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();

        

	}
	
}




options
A)A B A
B)A B A B
C)B B
D)A B

Correct answer is : A

Explanations :On the time of deserialization , the Serializable object not create new object. So constructor of class B does not called. 
A is not Serializable object so constructor is called.

Questions no -2 
What is the output for the below code ?

public class A {}

public class B implements Serializable  {
	A a = new A();
	public static void main(String... args){
		B b = new B();
		try{
			FileOutputStream fs = new FileOutputStream("b.ser");
			ObjectOutputStream os = new ObjectOutputStream(fs);
			os.writeObject(b);
			os.close();
			
		}catch(Exception e){
			e.printStackTrace();
		}
		
	}

}




options
A)Compilation Fail
B)java.io.NotSerializableException:  Because class A is not Serializable.
C)Run properly
D)Compilation Fail :  Because class A is not Serializable.

Correct answer is : B

Explanations :It throws java.io.NotSerializableException:A  Because class A is not Serializable.
When JVM tries to serialize object B it will try to serialize A also because (A a = new A()) is instance variable of Class B.
So thows NotSerializableException.

Questions no -3 
What is the output for the below code running in the same JVM?

public class A implements Serializable {
	transient int a = 7;
	  static int b = 9;

}

public class B implements Serializable  {
	
	public static void main(String... args){
		A a = new A();
		try {
		      ObjectOutputStream os = new ObjectOutputStream(
		         new FileOutputStream("test.ser"));
		      os.writeObject(a);  
		      os. close();
		      System.out.print( + + a.b + " ");

		      ObjectInputStream is = new ObjectInputStream(new FileInputStream("test.ser"));
		      A s2 = (A)is.readObject();
		      is.close();
		      System.out.println(s2.a + " " + s2.b);
		    } catch (Exception x) 
		    {
		    	x.printStackTrace();
		    }

	}

}




options
A)9 0 9
B)9 7 9
C)0 0 0
D)0 7 0

Correct answer is : A

Explanations :transient variables are not serialized when an object is serialized.
In the case of static variable you can get the values in the same JVM.