OLLSCOIL NA héireann THE NATIONAL UNIVERSITY OF IRELAND COLÁISTE NA hollscoile, CORCAIGH UNIVERSITY COLLEGE, CORK. Summer Examination 2013

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1 OLLSCOIL NA héireann THE NATIONAL UNIVERSITY OF IRELAND COLÁISTE NA hollscoile, CORCAIGH UNIVERSITY COLLEGE, CORK Summer Examination 2013 CS5015 Object-oriented Software Development Prof. Ian Gent Prof. Barry O Sullivan Mr. Adrian P. O'Riordan Time: 3 Hours Answer Question 1 and any three of remaining four questions Total = 140 marks Do not write answers on exam paper Page 1 of 7

2 Instructions for Question 1: There are a total of 50 marks for this multiple-choice question; each part is worth two marks. There is one correct answer (a., b., c., or d.) for each question. Write all your answers in an answer book, e.g. (i) b., (ii) d., etc. Question 1. (i) Java was developed by a team led by... a. James Gosling at Sun Microsystems (now Oracle); b. Bill Gates at Microsoft; c. Steve Jobs at Apple; d. Bjarne Stroustrup at AT&T. (ii) The JDK command to run an executable JAR file account.jar is a. java account b. java jar account.jar c. jar account.jar d. jar account (iii) What is the filename extension for Java bytecode files? a..exe b. no filename extension c..java d..class (iv) In Java, 10 / 2 evaluates to a. an int with the value 0; b. a double with the value 5; c. a double with the value 0; d. an int with the value 5. (v) Which one of the following is an illegal variable declaration in Java? a. char alpha; b. char α; c. char 1alpha; d. char ALPHA; (vi) Which of the following cannot be a return type? a. JButton b. public c. int d. void (vii) Which of the following is not a valid comment in Java? a. /* comment here */ b. // comment here c. /* // comment here */ d. /* /* comment here */ */ Page 2 of 7

3 (viii) Which one of these does not correctly declare and initialize a Boolean variable? a. boolean b = new Boolean(true); b. boolean b = true; c. boolean b = "true"; d. boolean b = new Boolean("true"); (ix) The class Object doesn t contain which one of the following methods? a. String tostring() b. boolean equals(object obj) c. int hashcode() d. void paintcomponent(graphics g) (x) What is the value of the calc variable after this statement? double calc = 5 / 1 * 2.0; a. 10.0; b. 5.0; c. 2.0; d (xi) Consider the following code snippet and determine what is displayed. String waterfall = "Snoqualmie Falls"; System.out.print(waterfall.charAt(waterfall.length() - 1)); a. e; b. s; c. S; d. nothing it generates an exception. (xii) Which one of these declarations will generate a compile time error? a. char[] vowels = "aeiou".tochararray(); b. String vowels = "aeiou"; c. String vowels = new String("aeiou"); d. char[] vowels = "aeiou"; (xiii) Assuming you create a class Dimension and implement a single constructor taking one argument, then the expression new Dimension() will... a. generate a compile time error; b. generate a run-time error; c. create a default constructor for Dimension and call it; d. fill in a default value for the argument and call the one argument constructor; (xiv) The Java expression "abc" + "def" will evaluate to... a. a String with the value abcdef; b. a String with the value defabc; c. will generate an InputMismatchException. d. an int with the value 6. Page 3 of 7

4 (xv) Java uses the keyword to reference an object s parent object. a. super b. self c. this d. object (xvi) What would be the output after running the following program? public class Tester{ private String str = "Test"; public Tester(String str) { this.str = str; public String getstr() { return str; public static void main(string[] args){ Tester t1 = new Tester("Test1"); Tester t2 = new Tester("Test2"); t1 = t2; System.out.print(t1.getStr()); a. Test; b. Test1; c. Test2; d. Tester. (xvii) Assuming you create a class called Star with no user-defined constructor then the code new Star() will: a. Generate a compile time error; b. Generate a run time error; c. Create a reference to a Star object; d. Create a Star object. (xviii) What is the effect of attempting to compile and run the following program? public class StartItUp { public void starter() { System.out.println("Vroom"); public static void main(string[] args) { StartItUp siu = new StartItUp(); siu.starter(); a. Doesn t compile; b. Compiles, runs, and doesn t display anything, c. Compiles, runs, and displays Vroom!; d. Compiles, but gives a run-time error; (xix) What are inner classes also know as? a. anonymous classes; b. nested classes; c. superclasses; d. subclasses. Page 4 of 7

5 (xx) Assuming you have a reference to a Graphics object called g, the code below will draw a line. What colour is the line? g.setcolor( new Color(0, 255, 0)); g.drawline(0, 0, 100, 100); a. red; b. green; c. blue; d. grue. (xxi) Assuming you have a reference to a Graphics object called g, which statement will draw an outline of a circle of radius 10 with the upper-left corner (of its bounding box) at coordinates (20, 20)? a. g. drawoval(20, 20, 10); b. g. drawoval(20, 20, 10, 10); c. g. drawoval(20, 20, 20); d. g. drawoval(20, 20, 20, 20); (xxii) Which method call sets the font to Helvetica 20 point bold? a. setfont("helvetica", Font.BOLD, 20); b. setfont(font("helvetica", Font.BOLD, 20)); c. setfont(new Font("Helvetica", Font.BOLD, 20)); d. setfont(new Font("Helvetica", BOLD, 20)); (xxiii) If a class implements ItemListener then it needs to implement what method? a. actionperformed(actionevent e) b. itemstatechanged(itemevent e) c. valuechanged(listselectionevent e) d. getactioncommand() (xxiv) Which one of these statements about the Swing widget toolkit is true? a. Swing completely replaces the older AWT; b. Swing components are not part of the Java Standard Edition; c. Swing components are all heavyweight components; d. Swing has lightweight components such as JPanel. (xxv) The getsource() method as defined in EventObject can be used to... a. determine the source of an exception or error; b. determine which component generated an event; c. return the value of the field called source; d. determine which type of event was generated. Page 5 of 7

6 Question 2. (Total of 30 marks for this question) (i) Write a Java program that extracts the extensions from filenames. It should read in a filename from the console and then displays the file extension also to the console. The file extension is the last part of the filename after the final dot. The program should be able to handle files with multiple dot characters, for example input of file.name.txt should return txt. The program should ask the user if he/she has another filename to parse either repeating or terminating. Note there is no requirement to check if such a file actually exists. (15 marks) (ii) Write a Java program to play the game of Rock-Paper-Scissors. The program should ask the use to choose rock, paper or scissors (via the console input). The program should randomly pick one for the computer opponent. Determine the winner and display on the console output or repeat if there is a tie. Aide-Mémoire: The rules of the game are as follows: rock defeats scissors; scissors defeats paper; and paper defeats rock. If both players choose the same the game is tied. (15 marks) Marks will be given for good program design, code layout, and choice of identifiers as well as a satisfactory implementation of the requirements above. No marks will be given for comments, test code or the inclusion of extra functionality not described above. Question 3. (Total of 30 marks for this question) An abstract class Socket should act as a blueprint for the following types of network connections, TCP and UDP. A socket has a port number. Implement a send() method in Socket that outputs "Sending data!". Create an interface called Reliable with the single method guarantee(). TCP implements Reliable. Implementations of the guarantee() method should display the simple message Delivery confirmed. Provide one-argument constructors for TCP and UDP (which set the port number). Define a list of 4 sockets. Create a TCP connection and a UDP connection and add them to this list. Call the send() and guarantee() methods where appropriate. Write classes in Java to implement this system. The use of object-oriented structures such as inheritance will gain much higher marks. Marks will be given for good program design, code layout, and choice of identifiers as well as a satisfactory implementation of the requirements above. No marks will be given for comments, test code or the inclusion of extra functionality not described above. Question 4. (Total of 30 marks for this question) Write a Java program to implement the GUI shown below. When the user types an amount in Euro in the first text input box and an exchange rate into the second, and then clicks the button (CONVERT!), a Dollar equivalent of the amount should appear in the third text box. This result should not be editable by the user. Page 6 of 7

7 Concentrate on creating the components, adding them and activating them. Use default colours and fonts. The screenshot is an example you do not have to replicate that exact layout or positioning. Keep answer short. Marks will be given for good program design, code layout, and choice of identifiers as well as a satisfactory implementation of the requirements above. No marks will be given for comments or the inclusion of extra functionality not described above. Question 5. (Total of 30 marks for this question) (i) Oracle has various editions of Java for different application environments. List four of these and briefly describe two. (5 marks) (ii) List five core language changes that were introduced with Java 5 and briefly state how they benefit developers. (5 marks) (iii) What is the Java virtual machine (JVM)? Explain the role played by bytecode in the JVM. What is the principle advantage of this virtual machine approach? (5 marks) (iv) Some educators consider Java to be a poor choice of language for introductory programming. Give two arguments either supporting or refuting this position. (2 marks) (v) Multiple inheritance is not supported in Java. Give two alternatives available to Java programmers who desire this capability. (2 marks) (vi) Explain what is meant by a GUI layout manager. Give an example of a Java layout you are familiar with and briefly outline how it lays out widgets. (4 marks) (vii) List four features of a Java IDE such as DrJava that make the programmer s life easier as opposed to using only a simple text editor and the command line JDK tools. (4 marks) (viii) What kinds of errors or bugs are trapped by exception handling at runtime? What kinds of error are not trapped? What popular developer tool deals with these kinds of problems? (3 marks) Page 7 of 7