EXAMINATION FOR THE DIPLOMA IN INFORMATION TECHNOLOGY; YEAR 2

Size: px

Start display at page:

Download "EXAMINATION FOR THE DIPLOMA IN INFORMATION TECHNOLOGY; YEAR 2"

Jason Barton
5 years ago
Views:

1 FACULTY OF SCIENCE AND TECHNOLOGY EXAMINATION FOR THE DIPLOMA IN INFORMATION TECHNOLOGY; YEAR 2 SAMPLE QUESTION

2 Question 1 A class called TV is required by a programmer who is writing software for a retail outlet. An object of the class TV will consist of a stock number, the make of the TV, the screen type (a character, either 'W' or 'R', meaning "widescreen" or "regular") and the price of the TV. The first three of these will need to be set only at the time an object is created. The price will also be set at the time of creation, but may need to be changed during the TV s lifetime. It will be necessary to have a means of reading the values of all the above data items. A method should also be provided which accepts the rate of tax (a double) as input, and returns the amount of tax to be paid. This is calculated as follows: tax price rate of tax 100 The TV class is shown in the below UML diagram: TV stockno : String make : String screentype : char price: double TV(String, String, char, double) setprice(double) getstockno(): String getmake(): String getscreentype(): char getprice(): double i) Write the code of the TV class in Java (18 marks) ii) Write a Java statement to create a new TV object, tv1, with the following details: stock number: S101 make: Elba type of screen: Regular price:

3 c) Briefly explain the key difference that distinguish between: i) class field and instance field (3 marks) ii) overriding method and overloading method (3 marks) iii) early binding and late binding (3 marks) d) Name THREE(3) classes of Unchecked Exception in Java. Explain with an example how each of the exception class will be thrown. (9 marks) Question 2 a) The following Java code contains some errors. Identify the errors, name the line number and rewrite the code with the errors corrected. (10 marks) public class Student { // 1 public void Student(String sid, String name) { // 2 setid(sid); // 3 setname(name); // 4 // 5 // 6 public setname(string _name) { // 7 name = _name; // 8 // 9 // 10 public void getname() { // 11 return name; // 12 // 13 // 14 public void setid(sid) { // 15 sid = sid; // 16 // 17 // 18 public String getid() { // 19 return sid; // 20 // 21 // 22 private String name; // 23 private String sid; // 24 // Student class // 25 public class StudentTester { // 26 public static void main(string[] args) { // 27 Student s = Student("BIS2009", "Michael"); // 28 s.setname(michael Lee); // 29 println("the student is " + s.name + "\n" // 30 + "The ID is " + s.getid); // 31 // StudentTester class // 32 b) Write a try/catch block which throws an Exception if the value of variable X is less than zero. The exception should be an instance of Exception with the message Error: Negative value in X coordinate. When it is caught, print out the error message using getmessage(). 2 (5 marks)

4 c) Compare and contrast abstract classes and interfaces. When would you use an abstract class? When would you use an interface? (6 marks) Question 3 a) Determine the output of the following program: (5 marks) public class ExceptionExercise { public void method1(int M) { try { System.out.println("Entering try block"); method2(m); System.out.println("Exiting try block"); catch (Exception e) { System.out.println("ERROR: " + e.getmessage()); finally { System.out.println("Exiting finally block"); public void method2(int M) { if (M > 100) { try { throw new Exception("Value is too large. : " + M); catch (Exception e) { System.out.println("Entering catch block 2"); throw e; finally { System.out.println("Executing finally block 2"); public static void main(string argv[]) { ExceptionExercise ex = new ExceptionExercise(); ex.method1(500); // ExceptionExercise b) Given that: (10 marks) public interface Installment { public double calculatefee(); Create a class named WeeklyInstallment with the following requirements: It implements the above Installment interface. It has 2 private attributes: amount of type double and noofweeks of type integer. It consists of a constructor which takes two parameters that initialize the amount and noofweeks attributes. It will implement calculatefee method which returns the balance due on the 5% annual interest rate based on the following formula: Balance Due = (amount * 1.05) * noofweeks/52 3

5 c) Describe TWO(2) benefits and TWO(2) limitations of Object Oriented Programming in Java. d) Explain the differences of the access modifiers: public, private and protected. (6 marks) Question 4 Consider the following codes: Person.java package org.app.model; import org.oop.model.dateofbirth; class Person { private String name; private String id; private DateOfBirth dob; private static int numberofperson = 0; public Person(String name, String id, DateOfBirth dob) { this.name = name; this.id = id; this.dob = dob; numberofperson++; public String getname() { return name; public String getid() { return id; public DateOfBirth getdateofbirth() { return dob; protected static int getnumberofperson() { return numberofperson; // End of Student class Student.java package org.app.model; import org.oop.model.dateofbirth; class Student extends Person { private String studentid; Student(String name, String id, DateOfBirth dob) { super(name, id, dob); public Student(String name, String id, DateOfBirth dob, String studentid) { this(name, id, dob); setstudentid(studentid); public String getstudentid() { return studentid; public void setstudentid(string studentid) { 4

6 this.studentid = studentid; // End of Student class a) Refer to the Student.java above, briefly (i) Describe the differences between this(...) and super(...) at the line 13 and 8 respectively. (ii) Explain the reasons of this(...) and super(...) invoked explicitly at the line 13 and 8 respectively. c) Refer to the Person.java above, briefly explain the reasons of having this keyword at the line 11. ~ END OF PAPER ~ 5

Week 5-1: ADT Design

Week 5-1: ADT Design Part1. ADT Design Define as class. Every obejects are allocated in heap space. Encapsulation : Data representation + Operation Information Hiding : Object's representation part hides,