York University AS/AK/ITEC 2610 3.0 All Sections OBJECT-ORIENTED PROGRAMMING Midterm Test Duration: 90 Minutes This exam is closed textbook(s) and closed notes. Use of any electronic device (e.g., for computing and/or communicating) is NOT permitted. Do not un-staple this test book any detached sheets will be discarded. Answer all questions in the space provided. No additional sheets are permitted. (Note: a blank page has been provided at the back of this test book that you may use for rough work; do not detach it) Work independently. The value of each question is indicated. The total value of all questions is 100. Write your section letter, your name and student number in the space below. NOTE: YOU MAY USE PEN OR PENCIL, BUT ANSWERS IN PENCIL WILL NOT BE CONSIDERED FOR RE-GRADING. Section (A/B): Surname: Given Names: Student Number: A (15) B (15) C (30) D(40) Total (100) 1
Part A (15 points) Consider the following (partial) API of two classes: class Department Department(String name, int budget) Parameters: name - name of the department budget - budget of this department void assign(employee who) Parameter: who - the employee to be assigned to this department int getheadcount() Returns: the number of employees in this department int getbudget() Returns: the budget of this department void changebudget(int delta) Increase or decrease the budget of this department by the passed amount. Delta is the increment or decrement, not the new budget. Parameter: delta - change the budget by adding this amount to it (to reduce budget, provide a negative amount). class Employee Employee(String name,int rank) Parameters: name - name of the employee rank - the rank (level) of the employee Develop the Java application App whose main method performs the following tasks, in the order shown: 1. Create a department called "R&D" with budget 2,000,000. 2. Create an employee John whose rank is 3. 3. Create an employee Debbie whose rank is 2. 4. Assign both John and Debbie to the R&D department 5. Determine the head count of the R&D department by using a method, and store it in some variable count. 6. If count is greater than 10, increase the department budget by 5%, otherwise reduce it by 2%. Note that it is OK to use the above magic numbers no need to store them as constants. 2
public class App{ public static void main(string[] args){ 3
Part B (15 marks) Write the 10-lines output of the program Bird.java shown below. interface Silly { public void narf(); public void poit(silly s); public class Bird implements Silly { public static void main(string args[]) { System.out.println("zero"); Silly s = new SillyBird(1); Silly s2 = new Loony(); s.poit(s2); s2.poit(s); System.out.println("zymurgy"); public Bird() { this(0); System.out.println("zircon"); public Bird(int i) { System.out.println("zanzibar"); public void narf() { System.out.println("zort"); public void poit(silly s) { s.narf(); class SillyBird extends Bird { public SillyBird() { System.out.println("duchess"); public SillyBird(int i) { super(i); public void narf() { System.out.println("drum"); super.narf(); class Loony extends SillyBird { public Loony() { System.out.println("stupendous"); public void narf() { System.out.println("snark"); 4
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PART C (30 marks) Multiple-Choice Questions. Circle the correct answers. Each question has only one correct answer unless specifically stated otherwise. Each question is worth 2 marks. 1) If a subclass does not explicitly call one of the superclass constructors, the default superclass constructor is called automatically. a) TRUE b) FALSE 2) Components in a GridLayout format can have different sizes. a) TRUE b) FALSE 3) Which 2 statements are true about an abstract class? (circle both) a). It can not be instantiated. b). It can not be extended. c). It can not be declared public. d). It may not have abstract methods. e). It can not be overridden. 4) Given a JLabel label and a JPanel panel with border layout, which of the following statements would you use to place the label at the top of the panel? a). panel.add(label, NORTH); b). label.add(panel, NORTH); c). panel.add(label, BorderLayout.NORTH); d). panel.add(label, BorderLayout.TOP); e). panel.add(label, TOP); 5) Which is the default LayoutManager for a JFrame? a) GridLayout b) FlowLayout c) CardLayout d) BorderLayout e) there is no default LayoutManager for a JFrame 6) In using the GridLayout, adding space between components in a container can be accomplished best by: a) including JButtons that have no names and thus will appear invisible. b) adding invisible components. c) inserting IconImages of blank images. d) specifying the spaces in pixels through the GridLayout constructor 7) In calling the method actionperformed (ActionEvent event) event is: a) an interface. b) a GUI component. c) an object. d) a listener. e) a reference to an existing object. 6
8) In order to display three components vertically in a container, you could use which 2 layout managers? (circle both) a) CardLayout b) GridLayout c) BorderLayout d) FlowLayout e) You could use any of the above. For the next 3 questions, consider the following class definition: public class AClass { protected int x; protected int y; public AClass(int a, int b){ x = a; y = b; public String tostring( ){ return x= + (++x) + \ny= + (y++) ; 9) Consider that you want to extend AClass to BClass. BClass will have a third instance data, int z. Which of the following would best define BClass' constructor? a) public BClass(int a, int b, int c){ super(a, b, c); b) public BClass(int a, int b, int c){ x = a; y = b; z = c; c) public BClass(int a, int b, int c){ z = c; d) public BClass(int a, int b, int c){ super(a, b); z = c; e) public BClass(int a, int b, int c){ super( ); 10) If the driver has the lines: BClass o = new BClass (1,2,3); System.out.println(o); the first line of the output is: 7
a) x=1 b) x=1 \n y=2 c) x=2 \n y=3 d) x=2 e) nothing 11) For the same driver the second line of output is: a) y=1 b) x=1 \n y=2 c) y=2 d) y=3 e) nothing For the next 4 questions, use the following partial class definitions: public class A{ public int x; private int y; protected int z;... public class B extends A { protected int a; private int b;... public class C extends A{ private int q;... 12) Which of the following is true with respect to classes A, B, and C? a) C is a subclass of B, and B is a subclass of A b) C and B are both subclasses of A c) A and B are both subclasses of C d) A is a subclass of B and C 13) Which of the following lists of instance variables are accessible in class B? a) x, y, z, a, b b) x, y, z, a, b, q c) x, y, z, b d) x, z, a, b e) x, z, a, q 14) Which of the following lists of instance data are accessible in class C? a) a, q b) x, y, z, a, q c) x, z, q d) z, a, q e) x, y, z, q 8
15) If you change the declaration of class C to be public class C extends B which of the following lists of instance variables are accessible in class C? a) x, y, z, a, b b) x, y, z, a, b, q c) x, y, z, b d) x, z, a, b e) x, z, a, q PART D (40 marks) Write the Java applet and the html file corresponding to the GUI shown below. The user starts by entering the results of a large number of students. For each student the user enters the name and the mark in the two textfields and then clicks on the Enter student data button. After finishing the data entry the user clicks on the other two buttons to produce the class average (truncated as an integer) and the name of the student with the highest mark. 9
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