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

Choose the appropriate true statement among the given options with reference to C++ programming.

  1. Friend function of a class cannot access private members of the given class.

  2. It is not mandatory to have a pure virtual function(s) in an abstract class.

  3. We can create object for an abstract class.

  4. If a class inherits abstract class and doesn't implement pure virtual functions of base class, then derived class also becomes abstract class.

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

This option is true because the derived class doesn't implement all pure virtual functions of the abstract class(base class) it turns to abstract class itself. Again we have to inherit the derived class to another derived class where we must implement all the pure virtual functions. If we don't implement at present derived class it also turn out to abstract class. Finally an abstract class should be followed by a class where all implementations of pure virtual functions are done completely.

Multiple choice

Identify the type of inheritance used in the following C++ code snippet.

class A { }; class B:public A { }; class C:public A { }; class D:public A { };

  1. Multiple inheritance

  2. Single or simple inheritance

  3. Hierarchical inheritance

  4. Multilevel inheritance

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

Given code snippet contains single base class (A) nd three derived classes(B,C,D) from base class (A). It depicts hierarchical inheritance where a single base class is inherited by two or more derived classes. This option is true.

Multiple choice

With the object oriented (OO) approach, an object encapsulates, or _____ a programmer.

  1. carries out, the details of an object for

  2. hides, the details of an object from

  3. reveals, the details of an object to

  4. extends, the details of an object beyond

  5. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In object-oriented programming, encapsulation means an object hides its internal implementation details from the programmer, exposing only necessary interfaces through public methods. This information hiding is a core principle that protects data integrity and reduces complexity.

Multiple choice

Why is there a need for virtual base class in hybrid/diamond inheritance? Multiple inheritance: more than one class is derived from single base class. Multilevel inheritance: single class is derived from many base classes.

  1. To avoid ambiguity

  2. For reusability

  3. For faster processing

  4. None of the above

  5. All 1, 2 and 3
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Virtual base class is used to reduce ambiguity, it cannot be used for faster processing and reusability.

Multiple choice

Which of the following is not a characteristic of Object Oriented programming?

  1. Data is hidden and cannot be accessed by external functions.

  2. Follows bottom-up approach in program design.

  3. New data and functions cannot be added whenever necessary.

  4. Program is divided into what are known as objects.

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

New data and functions can be added whenever necessary. For e.g. for(int i=0;i<4;i++) is valid in C++.

Multiple choice

What is the difference between function overloading and function overriding? a) In overloading multiple functions are available with same name, while in overriding single function is rewritten. b) Function overloading is possible in any program while function overriding is possible in inheritance. c) In overriding both functions must have same signature. In overloading multiple functions have same name but different arguments.

  1. Only a

  2. Both a and b

  3. All a, b and c

  4. Both are same

  5. Both b and c
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In overriding both functions must have same signature or prototype. In overloading multiple functions have same name but different arguments like different number of arguments and different type of arguments.

Multiple choice

Function overloading: static polymorphism is achieved by function overloading. Which of the following is not allowed in function overloading?

  1. Same function name with different number of arguments

  2. Same function name with different return type

  3. Same function name with different sequence of arguments

  4. Same function name with different types of arguments

  5. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Function overloading doesn’t uses the return type for identification of function, so option 2 is correct, e.g. int fun(int ,int);double fun(int,double); is not allowed in function overloading.

Multiple choice

Which of the following is not the characteristic of a constructor?

  1. Constructor has same name as that of the class.

  2. They don’t return value and are not of type void.

  3. Constructor can be private, public or protected.

  4. A class can have more than one constructor.

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

The constructors are always defined as public.

Multiple choice

Templates are used _________.

  1. as decision making statement

  2. to achieve generic programming

  3. to reduce ambiguity

  4. to achieve polymorphism in C++

  5. none of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Templates enable us to define generic classes and functions and thus provide support for generic programming.

Multiple choice

Why is there a need for virtual function when we access the function (having same name as that in base class) in derived class through the use of a pointer declared as pointer to the base class?

  1. We can not use the object name(with dot operator), as runtime polymorphism is achieved only when a virtual function is accessed through a pointer to the base class.

  2. We need to use single pointer variable to refer to the objects of different classes.

  3. When function is made virtual, C++ determines which function to use at run time based on the type of object pointed by the base class.

  4. All the above.

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

The necessity of virtual function is given by all the above 3 options, so option 4 is the correct answer.

Multiple choice

If there is a pointer p to object of a base class and it contains the address of an object of derived class and both classes contain a virtual member function xyz(), then the statement p->xyz(); will cause the version of xyz() in the ___________ class to be executed.

  1. derived class

  2. base class

  3. produces compile time error

  4. produces runtime error

  5. none of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Base b; Base *p; Derived d; p=&d; p->xyz(); as pointer is holding the address of derived class object and functions are defined virtual, derived class function xyz() is called.