First Name: AITI 2004: Make-up Exam 1 July 9, Last Name:

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1 First Name: AITI 2004: Make-up Exam 1 July 9, 2004 Last Name: Read Instructions Carefully! This is a 2 hour closed book exam. No calculators are allowed. Please write clearly if we cannot understand your answer, you will receive 0 points for that question. This exam has parts worth a total of points. Section 1: Control Structures (15 points) 1. (2 points) What does the following code print to the screen? int score = 75; String orange = "apple"; String apple = "orange"; if (score >= 75) { System.out.println(apple); System.out.println( orange ); orange orange 2. (2 points) What is the output of the following code? char grade = 'A'; switch (grade) { case 'A': case 'B': System.out.println("Excellent"); break; case 'C': System.out.println("OK"); break; default: System.out.println("Let's talk"); Excellent 3. (5 points) Write a while loop that calculates the product of the first 10 odd numbers. (Note: This is not the same as the product of the odd numbers from 1 to 10) int cnt = 0; int odd = 1; int prod = 1; while (cnt < 10) { prod *= odd; odd += 2; cnt++; Page 1 of 6 1

2 4. What is the output for the following segment of the code? a) (2 points) for (int i=10; i<=10; i++) { System.out.print(i+, ); 10, b) (4 points) for(int i=0; i<10; i++) { System.out.print(i+, ); i+=2; 0,3,6,9, Section 3: Methods and ArrayLists (10 points) 1. (5 points) Write a method, absolutevalue, which takes an int as an argument and returns the absolute value of the int. (For example, the absolute value of 5 is 5, the absolute value of -5 is 5, and the absolute value of 0 is 0.) public int absolutevalue(int num) { if (num >= 0) { return num; return num * -1; 2. (5 points) Write a method, absolutesum, which takes an int[] array as an argument and returns the sum of the absolute values of the numbers in that array. For example, calling absolutesum with the array {1, -1, 2, -2 as an argument should return the number 6. public int absolutesum(int[] nums) { int sum = 0; for (int i = 0; i < nums.length; i++) { sum += absolutevalue(nums[i]); return sum; Page 2 of 6 2

3 Section 4 Packages Access and Scope (5 poi nts) package examples; class Operations{ int a = 5; int square(int a) { this.a = a*a; return a; void print() { System.out.println(square(a)); System.out.println(a); What will the method print() print out? 5 25 Page 3 of 6 3

4 Section 5 Static and Final (5 points) Below is the partial implementation of a class that has a library of methods to perform mathematical computations. The implementation of one of the methods, areaofcircle, is shown. package math; public class DoMath{ //FIELDS // Constant that stores the value of pi public static final double PI = ; // method that returns the area of a circle with radius r public static double area(double r){ return PI * r * r; We also have another class in the Math package called Circle. This class models a circle and has a constructor that takes in the radius of the circle. package math; public class Circle { //fields // stores the radius of the circle public double radius; //constructor that initializes the radius field public Circle(double r) { radius = r; We now want you to complete the implementation of the UseCircle class in the same package below. package math; public class UseCircle{ // TODO: Add a main method that creates a Circle object // with radius 2.0 and prints out the area of the circle // using the classes defined above Circle circle = new Circle(2.0); System.out.println( The circle with radius + circle.radius + has an area of: + DoMath.area(circle.radius)); Page 4 of 6 4

5 Section 6 Classes (15 points) On the next page, you will write a hierarchy of classes to represent employees in a package called payroll. We want to be able to access all the classes and methods that you write from any package. First, create an Employee class. An employee has the following properties, which cannot be accessed outside of the class: first name of the employee and last name of the employee. Write a constructor that accepts the first name and last name of the employee as arguments and sets the class properties to those values. Add a method called description that returns a string containing the full name of the person. For example, if the first name is John and the last name is Mensah, this method should return the string John Mensah. This method should be accessible from any package. Create a subclass of Employee called Manager. Manager has a salary that is initialized in the constructor and a getpay method that returns the salary. Add a description method to Manager which returns a String containing the result of Employee's description method, followed by the result of the getpay method. For example, the description method of a Manager with the name "Samuel Kojo" and a cedis salary would return the String "Samuel Kojo ". Create another subclass of Employee called Engineer. Engineer has two new fields (wage and hours worked) that are initialized in the constructor and a getpay method that returns a double containing the product of wage and the hours worked. Add a description method to Engineer which returns a String containing the result of Employee's description method, followed by the result of the getpay method. For example, the description method of an Engineer with the name Tamara Mensah, wage of 10 cedis and 2 hours worked would return the String "Tamara Mensah 20.0". package payroll; public class Employee { private String firstname; private String lastname; public Employee(String fname, String lname) { this.firstname = fname; this.lastname = lname; public String description() { return firstname + lastname; Page 5 of 6 5

6 package payroll; public class Manager extends Employee { private double salary; public Manager(String fname, String lname, double s) { super(fname,lname); this.salary = s; public double getpay() { return salary; public String description() { return super.description() + + getpay(); package payroll; public class Engineer extends Employee { private double wage; private double hoursworked; public Engineer(String fname, String lname, double w, double hw) { super(fname,lname); this.wage = w; this.hoursworked = hw; public double getpay() { return wage * hoursworked; public String description() { return super.description() + + getpay(); Page 6 of 6 6