Computer Knowledge

Object-Oriented Programming

2,686 Questions

Object-oriented programming questions test core computer science concepts like classes, inheritance, polymorphism, and encapsulation. The focus includes Java program structures, method overloading, and memory allocation for objects. This topic is essential for technical sections in various recruitment tests.

Java class definitionsMethod overriding rulesPolymorphism conceptsGeneric type parametersMemory allocation in objects

Object-Oriented Programming Questions

Multiple choice

Which of the following is/are difference(s) between class and interface? (a) Class can be instantiated, while interface cannot. (b) Class is a collection of data members and methods, while Interface consists of constants and method declarations. (c) Any class can extend another class using keyword extends, while interfaces are implemented using keyword implements.

  1. Only (a)

  2. Only (a) and (b)

  3. Only (b) and (c)

  4. All (a), (b) and (c)

  5. None of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All a,b and c are correct.

Multiple choice

What is the use of Super keyword in Java?

  1. Used for inheritance

  2. Allows child class to call parameterized constructor of the class

  3. Used for making a function inline

  4. Used for making class or function template

  5. Allows parent class to call parameterized constructor of child class
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In constructor calling, default constructor of parent class gets automatically called. Super keyword allows child class to call parameterized constructor of the parent class.

Multiple choice

Which of the following is/are not the difference(s) between Abstract Class and Interfaces? (a) A class can implement several interfaces but may extend only one abstract class. (b) No constructors are provided by interfaces, while abstract class provides constructors. (c) Variables in interfaces must me public, static or final. There is no such restriction in abstract class.

  1. Only (a)

  2. Only (a) and (b)

  3. Only (b) and (c)

  4. All (a), (b) and (c)

  5. None of the above
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

None of the above s correct answer as all a,b,c are the differences between interface and abstract class.

Multiple choice

How the further can inheritance be stopped?

  1. Using static modifier

  2. Using private access specifier

  3. Using final modifier

  4. Using volatile modifier

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Final modifier can be used with class, data member and methods. A class cannot be inherited when declared as final.

Multiple choice

Which of the following restrictions to static method is not correct?

  1. They can only call static methods.

  2. They must only access static data.

  3. They cannot refer to 'this' keyword.

  4. They cannot refer to 'super' keyword.

  5. Static data cannot be initialized.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This is not the correct restriction as static data can be initialized to any value.

Multiple choice

What is the other name used for a base class?

  1. Child class

  2. Subclass

  3. Derived class

  4. Parent class

  5. Array class
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A parent class is the closest class that we derive to create the one we are referencing as the child class.