POLYTECHNIC OF NAMIBIA SCHOOL OF COMPUTING AND INFORMATICS DEPARTMENT OFCOMPUTER SCIENCE COURSE NAME: OBJECT ORIENTED PROGRAMMING

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1 @ ゥM セM セM セMLMQ POLYTECHNIC OF NAMIBIA SCHOOL OF COMPUTING AND INFORMATICS DEPARTMENT OFCOMPUTER SCIENCE COURSE NAME: OBJECT ORIENTED PROGRAMMING COURSE CODE: OOP521S NQF LEVEL: 5 DATE: NOVEMBER 2014 DURATION: 2HOURS MARKS: 100 PAPER: THEORY 1'' OPPORTUNITY EXAMINATION QUESTION PAPER EXAMINER: MODERATOR: MR. MARSHALL GOREJENA DR. SHA WULU H. NGGADA INSTRUCTIONS 1. Write all your answers in the answer booklet provided. 2. This paper consists of three sections; Section A, Band C. 3. Answer ALL questions in section A, section B and section C. 4. Begin each section on a new page. 5. Marks/scores per question are given in [ ]. 6. Do not use or bring into the examination venue books, programmable calculators, mobile devices and other material that may provide you withunfair advantage. Should you be in possession of one right now, draw the attention of the examination officer or invigilator. 7. Pol technic of Namibia's examination rules andre ulations a This paper consists of I I pages excluding this cover

2 SECTION A - Multiple Choice [50 marks] 1. Which one of these is a function of the Java Virtual Machine(JVM)? A. Translate Java byte code into a language the operating system understands B. Run a Java programme C. Convert a Java programme into an executable D. Link a Java programme to a database [I marks] 2. If we had an array which was represented by the following diagram, how would we reference the second element (the number 42)? Marks[]: A. Marks(!) B. Marks(2) C. Marks[!] D. Marks[2] [ 1 mark] 3. Assume you have a Java public class called BankAccount in a tile. What would you name the file in accordance with proper practice'' A. Bank.java B. BankAccount.java C. BankAccount.class D. publicclass.java 4. A data type that separates the logical properties lfom the implementation details is known as: A. External data type B. Permanent data type C. Abstract data type D. None of the above 5. The is-a relationship between classes is represent by: A. Composition B. Inheritance C. Encapsulation D. Instantiation 6. The difference between an array and an array list is that: A. An array can store more data than an array list; B. An array is of fixed size, while an array list is dynamic in size; C. An array list is indexed whilst an array not D. None of the above [I marks] 1

3 7. Only one of the following lines of code correctly declares a new String array with 5 clements. Which one is it? A. String names =new String[5]; B. String() names= new String(5); C. String[] names= new String [5]; D. String [ ] names = new [5] String; 8. What relationship exists between class Foo and class Bar? public class Foo [I marks] public class Bar Foo fool= new Foo( ); ) A. Composition B. Inheritance C. Encapsulation D. Instantiation [I marks) 9. Study the class below : public class Cat private String name; public Cat( ) ) public Cat( String name) this. name = name Which of the following lines would conectly instantiate the class? 1. Cat catl=new Cat[" Kitty"]; 11. Cat catl=new Cat(); 111. Cat catl=new ("Kitty"); iv. Cat catl=new Cat(" Kitty''); A. i and ii. B. i and iv C. ii and iv. D. ii and iii. 2

4 10. What key word is used by a class that you would use to come up with concrete methods of previously declared abstract methods? A. Inherits B. Implements C. Links D. Extends r 1 mark] 11. The two subclasses of the Throwable class are: A. Exception class and Error class B. Exception class and Object class C. Error class and RunTime Exception class D. Exception class and RunTime Exception class [1 marks] 12. Which exception occurs when you try to create an object of an abstract class or interface'' A. ClassNot FoundException B. lllega!accessexception C. InstatiationException D. NoSuchMethodException 13, Consider the statements: Statement A: The scope of the catch block is restricted to the statements in the preceding try block only. Statement B: A try block must have at least one catch block that follows it immediately. Which of the following options is true'' A. Statement A is true and statement B is false B. Statement A is false and statement B is true C. Both, statements A and B, are true D. Both, statements A and B, are false [I marks] 14. What is the access type of the methods declared in an interface? A. Default B. Private C. Public D. Protected 15. Which type of inheritance is supported by Java? A. Hierarchical inheritance B. Multiple inheritance C. Single level inheritance D. Multipath inheritance [1 marks] 3

5 16. Class fields arc usually written as private so that: A. The class looks very nice B. When objects are created they can reside well in the heap C. We can control how class data is accessed D. The objects can be usable in the application 17. The term static when used for a variable in a class means: A. Every object for that class will have its own copy of the variable B. There will be only one copy of that variable for all objects of that class and all objects share it C. The variable can be used to create objects D. Public variables [I marks] 18. Which concept of object-oriented programming is used in method overriding? A. Polymorphism B. Abstraction C. Encapsulation D. Inheritance II mark] 19. Variables that are shared by every instantiation of a class are called: A. Illegal B. Private variables C. Class variables or static variables D. Public variables [1 marks] 20. Once you write a constructor for a Java class it means: A. You must overload it B. You can no longer access the default constructor C. Your class must have parameters always D. You can instantiate objects nicely 21. The Unified Modelling Language(UML) diagrams are useful because: A. They must be used by programmers B. They give a clear picture of the attributes and methods in a class C. You cannot write the source code without them D. The programs will not work if you do not have them 22. Methods that you call with the class name are called: A. Public methods B. Static methods C. Non-static methods D. Private methods [I marks] 4

6 23. The Javadoc utility is used to: A. Compile the java programs B. Make java programs mn correctly C. Generate the Application Programming Interface for Java classes D. Generate websites for companies II mark] 24. The garbage collector is a Java program which: A. We use to compile programs B. is used to remove objects which are no longer referenced in memory C. is used to make executable jars for java applications D. is used to make the manifest files [I mark[ 25. Which three types of comments that can be made in Java? A. Paragraph comments, page comments and source code comments B. Javadoc tag comments, java comments and class comments C. Line comments, block comments and javadoc comments D. Object comments, class comments and methods comments @return are examples of: A. Javadoc comments B. Class attributes C. Constructors D. Javadoc tags 27. What arc static variables normally used for within a class'> A. Do any necessary calculations with objects B. Count all the class attributes within a class C. Make sure the java class can compile D. Make sure methods work correctly [!mark] 28. The method Integer.parselnt() is used to: A. Make the variables change to big integers B. Convert a string containing an integer to an object integer type C. Make life easy for java programmers D. None of the above 29. The new operator is used to : A. Make a new application B. Reserve enough memory and copy the address of an object and store it in a reference variable C. Create the methods for the class and make sure that the attributes are private D. Make a new website for the documentation of the java class you just created 5

7 30. The statement import java. uti!.* is used to: A. Import stars into the class B. Allow you to use the classes in the package java. uti! C. Enable you to use the JOptionPane class D. Make your application to print stars 31. We sometimes include the main method in a class not designed to be an application, for the purposes of : A. Creating the java documentation B. Making a package for the class C. Testing the functionality of that class D. Instantiating objects for that class 32. The tostring() method is used to convert: A. A character to a String B. An integer to a String C. A float to a String D. All of the above 33. Joining strings with a"+" is called: A. Chaining B. Parsing C. Linking D. Concatenation 34. The Throwable class is the sub class of: A. Exception class B. Error class C. Object class D. RunTimeExccption 35. Which keyword is used to define the constants in an interface? A. Super B. Public C. Private D. Final 36. What is used within square brackets to access clements of an array? A. A character B. A double C. An integer D. A string [!mark] 6

8 37. What is represented by array names? A. Values B. Functions C. References D. Allusions [ 1 mark] 38. When you initialise an array by giving values upon creation, you: A. Do not explicitly give the array a size B. Must also give the array a size C. Must make all the values zero blank or false D. Must make certain each value is different from the others 39. When you pass an array to a method, the method receives: A. A copy of the array B. A copy of the first element in the array C. The address of the array D. Nothing r 1 mark] 40. Object array elements are sorted according to: A. Object's field B. Object's methods C. Object's name D. Object's type 41. Which feature of OOP that means ignoring the non-essential details of an object and concentrating on its essential features? A. Polymorphism B. Encapsulation C. Abstraction D. Inheritance 42. Identify the type of relationship shared by the Gear and Automobile class in the given figure below : L_c_e_a_r j!---?'-.---,>1 Automobile A. Part-of B. Is-a C. Kind-of D. Has-a [!mark] 7

9 43. A collection of related classes in java is called: A. Packet B. Package C. Bundle D. Gaggle 44. We use the debugger to trace the execution of a Java application so that: A. We can create an executable jar for the program B. We can understand what the program does C. We can be able to generate the documentation D. it can be possible to count class objects 45. You send messages or information to an object through its: A. Methods B. Fields C. Classes D. Types r 1 mark] 46. Which of the following exceptions is raised when a number is divicled by zero? A. Nu llpointerexception B. ArithrneticExceptio n c. Arra yl ndex Ou tofbou nd sexccption D. NumberFormatException 47. When you declare an array: A. You always reserve memory for it in the same statement B. You might reserve memory for it in the same statement C. You cannot reserve memory for it in the same statement D. Your ability to reserve memory for it depends with the type of the array 48. Which of the following data types is not a temporary data type? A. Array B. Object C. Stack D. file r 1 mark] 11 mark] 8

10 49. What relationship exists between class A and class B? public class A public class B extends A SO. A. Composition B. Encapsulation C. Inheritance D. Instantiation Java can connect to a database using: A. JDBC B. SQL C. OBDC D. DNS I I mark] I I marks[ 9

11 SECTION B (True or False) [10 marks] 1. Method declaration is another name for method signature. True or False } 11 mark] 2. An instance variable is also known as a class variable True or False ) II mark] 3. Constructors and static methods can be declared abstract. True or False ) 4. Interfaces offer a capability requiring that unrelated classes implement a set of common methods. True or False } 5. All public and protected superclass members retain their original access modifier when they become members of the subclass. True or False ) 6. Arrays are passed to methods by value. I True or False } [I mark! 7. An individual primitive-type array element that is passed to a method and modi tied in that method will contain the modified value when the called method completes execution. True or False} II mark] 8. A constructor docs not necessarily need to have the same name as the class. True or False) 9. Polymorphism is a form of software reusability in which classes acquire the members of existing classes and embellish those classes with new capabilities. True or False) II mark] 10. An unchecked exception cannot be handled. True or False ) 10

12 SECTION C (Structured Questions) [40 marks] 1. Using appropriate examples explain how encapsulation differs from abstraction [5 marks] 2. Compare and contrast method overloading and method overriding [5 marks] 3. Explain the importance of implementing interfaces in Java [5 marks[ 4. Briefly discuss the use of exceptions and their importance. 15 marks] 5. (a) Write source code for the bank application with driver/main class BankApp and another class BankAccount, with instance variables AccountName and AccuuntBalance and the following methods deposit(), withdraw() which receives amount as a parameter and getbalance() which returns the balance to the screen. [18 marks] (h) Instantiate an object called custobj to test your class in (a) above. [2 marks] Fnd