Java Questions & Answers – Method overriding

This section of our 1000+ Java MCQs focuses on method overriding in Java Programming Language.

1. Which of this keyword can be used in a subclass to call the constructor of superclass?
a) super
b) this
c) extent
d) extends
View Answer

Answer: a
Explanation: None.

2. What is the process of defining a method in a subclass having same name & type signature as a method in its superclass?
a) Method overloading
b) Method overriding
c) Method hiding
d) None of the mentioned
View Answer

Answer: b
Explanation: None.

3. Which of these keywords can be used to prevent Method overriding?
a) static
b) constant
c) protected
d) final
View Answer

Answer: d
Explanation: To disallow a method from being overridden, specify final as a modifier at the start of its declaration. Methods declared as final cannot be overridden.
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4. Which of these is correct way of calling a constructor having no parameters, of superclass A by subclass B?
a) super(void);
b) superclass.();
c) super.A();
d) super();
View Answer

Answer: d
Explanation: None.

5. At line number 2 in the following code, choose 3 valid data-type attributes/qualifiers among “final, static, native, public, private, abstract, protected”

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  1. public interface Status
  2.    {
  3.         /* insert qualifier here */ int MY_VALUE = 10;
  4.    }

a) final, native, private
b) final, static, protected
c) final, private, abstract
d) final, static, public
View Answer

Answer: d
Explanation: Every interface variable is implicitly public static and final.
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6. Which of these is supported by method overriding in Java?
a) Abstraction
b) Encapsulation
c) Polymorphism
d) None of the mentioned
View Answer

Answer: c
Explanation: None.

7. What will be the output of the following Java program?

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  1.  class Alligator 
  2.  {
  3.   public static void main(String[] args) 
  4.    {
  5.    int []x[] = {{1,2}, {3,4,5}, {6,7,8,9}};
  6.    int [][]y = x;
  7.    System.out.println(y[2][1]);
  8.    }
  9.  }

a) 2
b) 3
c) 7
d) Compilation Error
View Answer

Answer: c
Explanation: Both x,and y are pointing to the same array.

8. What will be the output of the following Java program?

  1.    final class A 
  2.     {
  3.          int i;
  4.     }    
  5.     class B extends A 
  6.     {
  7.         int j;
  8.         System.out.println(j + " " + i);  
  9.     }    
  10.     class inheritance 
  11.     {
  12.         public static void main(String args[])
  13.         {
  14.             B obj = new B();
  15.             obj.display();     
  16.         }
  17.    }

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

Answer: d
Explanation: class A has been declared final hence it cannot be inherited by any other class. Hence class B does not have member i, giving compilation error.
output:

$ javac inheritance.java
Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
	i cannot be resolved or is not a field

9. What will be the output of the following Java program?

  1.   class Abc
  2.   {
  3.       public static void main(String[]args)
  4.       {
  5.           String[] elements = { "for", "tea", "too" };
  6.           String first = (elements.length > 0) ? elements[0]: null;
  7.       }
  8.   }

a) Compilation error
b) An exception is thrown at run time
c) The variable first is set to null
d) The variable first is set to elements[0]
View Answer

Answer: d
Explanation: The value at the 0th position will be assigned to the variable first.

10. What will be the output of the following Java program?

  1.     class A 
  2.     {
  3.         int i;
  4.         public void display() 
  5.         {
  6.             System.out.println(i);
  7.         }    
  8.     }    
  9.     class B extends A 
  10.    {
  11.         int j;
  12.         public void display() 
  13.         {
  14.             System.out.println(j);
  15.         } 
  16.     }    
  17.     class Dynamic_dispatch 
  18.    {
  19.         public static void main(String args[])
  20.         {
  21.             B obj2 = new B();
  22.             obj2.i = 1;
  23.             obj2.j = 2;
  24.             A r;
  25.             r = obj2;
  26.             r.display();     
  27.         }
  28.    }

a) 1
b) 2
c) 3
d) 4
View Answer

Answer: b
Explanation: r is reference of type A, the program assigns a reference of object obj2 to r and uses that reference to call function display() of class B.
output:

$ javac Dynamic_dispatch.java
$ java Dynamic_dispatch 
2

Sanfoundry Global Education & Learning Series – Java Programming Language.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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