Java Multiple Choice Questions & Answers on Inheritance for Freshers

1. Which of these keyword must be used to inherit a class?

a) super
b) this
c) extent
d) extends

Answer: d

2. Which of these keywords is used to refer to member of base class from a sub class?

a) upper
b) super
c) this
d) None of the mentioned

Answer: b

Explanation: whenever a subclass needs to refer to its immediate superclass, it can do so by use of the keyword super.

3. A class member declared protected becomes member of subclass of which type?

a) public member
b) private member
c) protected member
d) static member

Answer: b

Explanation: A class member declared protected becomes private member of subclass.

4. Which of these is correct way of inheriting class A by class B?

a) class B + class A {}
b) class B inherits class A {}
c) class B extends A {}
d) class B extends class A {}

Answer: c

5. Which two classes use the Shape class correctly? (Choose two.)

A. public class Circle implements Shape 
   {
    private int radius;
   }
B. public abstract class Circle extends Shape 
   {
    private int radius;
   }
C. public class Circle extends Shape 
   {
   private int radius;
   public void draw();
   }
D. public abstract class Circle implements Shape 
   {
    private int radius;
    public void draw();
   }
E. public class Circle extends Shape 
   {
    private int radius;
    public void draw()
    {
     /* code here */
    }
   }
F. public abstract class Circle implements Shape 
   {
     private int radius;
     public void draw() 
     { 
      /* code here */ 
     }
   }

a) B,E
b) A,C
c) C,E
d) T,H

Answer: a

Explanation: If one is extending any class, then they should use extends keyword not implements.

6. What is the output of this program?

1.     class A {

2.         int i;

3.         void display() {

4.             System.out.println(i);

5.         }

6.     }    

7.     class B extends A {

8.         int j;

9.         void display() {

10.             System.out.println(j);

11.         }

12.     }    

13.     class inheritance_demo {

14.         public static void main(String args[])

15.         {

16.             B obj = new B();

17.             obj.i=1;

18.             obj.j=2;   

19.             obj.display();     

20.         }

21.    }

a) 0
b) 1
c) 2
d) Compilation Error

Answer: c

Explanation: class A & class B both contain display() method, class B inherits class A, when display() method is called by object of class B, display() method of class B is executed rather than that of Class A.

7. What is the output of this program?

1.     class A {

2.         int i;

3.     }    

4.     class B extends A {

5.         int j;

6.         void display() {

7.             super.i = j + 1;

8.             System.out.println(j + " " + i);

9.         }

10.     }    

11.     class inheritance {

12.         public static void main(String args[])

13.         {

14.             B obj = new B();

15.             obj.i=1;

16.             obj.j=2;   

17.             obj.display();     

18.         }

19.    }

a) 2 2
b) 3 3
c) 2 3
d) 3 2

Answer: c

8. What is the output of this program?

1.     class A {

2.         public int i;

3.         private int j;

4.     }    

5.     class B extends A {

6.         void display() {

7.             super.j = super.i + 1;

8.             System.out.println(super.i + " " + super.j);

9.         }

10.     }    

11.     class inheritance {

12.         public static void main(String args[])

13.         {

14.             B obj = new B();

15.             obj.i=1;

16.             obj.j=2;   

17.             obj.display();     

18.         }

19.    }

a) 2 2
b) 3 3
c) Runtime Error
d) Compilation Error

Answer: d

Explanation: class contains a private member variable j, this cannot be inherited by subclass B and does not have access to it.

9. What is the output of this program?

1.     class A {

2.         public int i;

3.         public int j;

4.         A() {

5.             i = 1;

6.             j = 2;

7.  }

8.     }    

9.     class B extends A {

10.         int a;

11.         B() {

12.             super();

13.         } 

14.     }    

15.     class super_use {

16.         public static void main(String args[])

17.         {

18.             B obj = new B();

19.             System.out.println(obj.i + " " + obj.j)     

20.         }

21.    }

a) 1 2
b) 2 1
c) Runtime Error
d) Compilation Error

Answer: a

Explanation: Keyword super is used to call constructor of class A by constructor of class B. Constructor of a initializes i & j to 1 & 2 respectively.

10. What is the output of this program?

1.     class A {

2.         public int i;

3.         protected int j;

4.     }    

5.     class B extends A {

6.         int j;

7.         void display() {

8.             super.j = 3;

9.             System.out.println(i + " " + j);

10.         }

11.     }    

12.     class Output {

13.         public static void main(String args[])

14.         {

15.             B obj = new B();

16.             obj.i=1;

17.             obj.j=2;   

18.             obj.display();     

19.         }

20.    }

a) 1 2
b) 2 1
c) 1 3
d) 3 1

Answer: a

Explanation: Both class A & B have member with same name that is j, member of class B will be called by default if no specifier is used. I contains 1 & j contains 2, printing 1 2.