NATIONAL OPEN UNIVERSITY OF NIGERIA

UNIVERSITY VILLAGE, PLOT 91, CASDASTRAL ZONE, NNAMDI AZIKIWE EXPRESS WAY, JABI, ABUJA.
FACULTY OF SCIENCES
OCTOBER 2019 EXAMINATION

COURSE CODE: CIT383
COURSE TITLE: INTRODUCTION TO OBJECT-ORIENTED PROGRAMMING
COURSE CREDIT: 2 UNITS
TIME ALLOWED: 2 HOURS
INSTRUCTION: ANSWER QUESTION 1 AND ANY OTHER THREE (3) QUESTIONS

Question 1
(a) i. Discuss the concept of object as it relates to OOP? (3 marks)
ii. What are the effects of new operator and finalise () method on Java object. (2 marks)
(b) i. Mention two differences between the declarations of interfaces and abstract classes. (2 marks)
ii. Describe a typical abstract method for Java class. (2 marks)
(c) i. What is an instance variable? (2 marks)
ii. Mention two differences between local and instance variables. (2 marks)
(d) i. Briefly explain the concept of modular programming? (2 marks)
ii. State one advantage and disadvantage of modular programming. (2 marks)
(e) i. Briefly explain the difference between composition and aggregation with an example.
(3 marks)
ii. Briefly describe static method. (2 marks)
(f) Why is it illegal to use abstract keyword on static method? (3 marks)
[25 marks]

Question 2
(a) i. Define class within the context of Java programming concept? (4 marks)
ii. Briefly explain the general syntax for a class in OOP? (3 marks)
(b) Describe four (4) rules guiding the formation of abstract data type. (4 marks)
(c) Mention four (4) advantages of using interface in a program. (4 marks)
[15 marks]

Question 3
(a) i. Briefly describe message passing in pure OOP? (4 marks)
ii. List four examples of message passing styles. (2 marks)
(b) Describe the three (3) access modifiers that are explicitly declared by Java programmer?(3 marks)
(c) Write a Java class called FactorialFinder that computes and displays the factorial of a number. The class should declare and use a method called factorialCalculator, which should accept an integer number for the factorial computation and return the answer of the computation. (6 marks)
[15 marks]

Question 4
(a) i. Describe encapsulation as one of the concepts in OOP. (4 marks)
ii. Write a Java class named Student that has one-member field called height, which is double data type. The implementation of the class should encapsulate the member field. (3 marks)
(b) i. Briefly describe accessor and mutator methods? (3 marks)
ii. State two differences between constructor and other typical method. (3 marks)
(c) Differentiate between subclass and superclass. (2 marks)
[15 marks]

Question 5
(a) i. Explain inheritance within the context of OOP concept? (4 marks)
ii. List three (3) benefits of inheritance? (3 marks)
(b) i. What is a no argument constructor? (4 marks)
ii. Outline two (2) differences between a no argument and default constructors? (2 marks)
(c) Enumerate two (2) advantages of abstraction to programmer. (2 marks)
[15 marks]