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

It is desired to design an object-oriented employee record system for a company. Each employee has a name, unique id and salary. Every employee belongs to different categories and his salary is determined by his category. The functions getName, getld and computeSalary are required. Given the class hierarchy below, possible locations for these functions are:

(i) getld is implemented in the superclass (ii) getld is implemented in the suclass (iii) getName is an abstract function in the superclass (iv) getName is implemented in the superclass (v) getName is implemented in the subclass (vi) getSalary is an abstract function in the superclass (vii) getSalary is implemented in the superclass (viii) getSalary is implemented in the subclass

Choose the best design

  1. (i),(iv),(vi).(viii)

  2. (i),(iv),(vii)

  3. (i),(iii),(v),(vi),(viii)

  4. (ii),(v),(viii)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Employee ID and employee name are independent of subclasses; manager engineer or secretary, so these should be implemented in super class, but salary is part of employee dependent, so abstract get salary should be in super class and its actual implementation in subclass.

Multiple choice

Consider the following class definitions in a hypothetical Object Oriented language that supports inheritance and uses dynamic binding. The language should not be assumed to be either Java or C++, though the syntax is similar.

Class P {
  Class Q subclass of P {
    void f(int i) {
      void f(int i) {
        print(i);
        print(2 * i);
      }
    }
  }
}

Now consider the following program fragment: Px = new Q() Qy = new Q(); Pz = new Q(); x.f(1); ((P)y).f(1); z.f(1); Here ((P)y) denotes a typecast of y to P. The output produced by executing the above program fragment will be

  1. 1 2 1

  2. 2 1 1

  3. 2 1 2

  4. 2 2 2
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Multiple choice

Which of the following is the correct format of a Java program?

 
  1.   class abc {
   Public static void main(String args[]) {……………}
  }

  2.   class abc {
   public Static void main(String args[]) {……………}
  }

  3.   class abc {
   Public static void Main(String args[]) {……………}
  }

  4.   class abc {
   public static void main(String args[]) {……………}
  }
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The correct format for a Java program is as follows: class abc { public static void main(String args[]) { …………… } } Here, the keywords class, public and static must be in lower case. String is the class name.

Multiple choice

If there is a protected method within the Public class, then which of the following statements is correct?

  1. Protected method does not access the public method.

  2. Method is accessible from inside a class and a subclasses.

  3. Protected method is not allowed within the Public class.

  4. Method is accessible from inside the class and all the classes defined in the same package, where the class is defined itself.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Protected method is accessible from inside the class and all the classes defined in the same package, where the class is defined itself.