Appendices Attached (2 pages) Two Hours UNIVERSITY OF MANCHESTER SCHOOL OF COMPUTER SCIENCE QUESTION PAPER MUST NOT BE REMOVED FROM THE EXAM ROOM

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1 Appendices Attached (2 pages) COMP27010 Two Hours UNIVERSITY OF MANCHESTER SCHOOL OF COMPUTER SCIENCE QUESTION PAPER MUST NOT BE REMOVED FROM THE EXAM ROOM Object Oriented Programming 2 Date: Monday 19 th May 2008 Time: 14:00 16:00 Answer the 20 short questions in Section A (worth 60 marks) Answer ONE question from Section B (worth 20 marks) Answer ONE question from Section C (worth 20 marks) Note: Do not answer more than the required number of questions. Clearly cross out anything you do not wish to be marked. The use of electronic calculators is permitted provided they are not programmable and do not store text. [PTO]

2 Page 2 of 16 COMP27010 Section A Answer all questions 1. Java utilises class constructors. Answer the following questions with reference to a constructor. a) What is a constructor? (0.5 mark) b) What is the function of a constructor? (0.5 mark) c) How is a constructor called? Write a code fragment that instantiates an object, of type ClassA, by calling its constructor. (1 mark) 2. Given the Java interface code, ExampleInterface, specification below, answer the following: a) When an interface is implemented in a specific class, what does the interface ensure the class contains? (1 mark) b) What does the compiler assume if a class uses an interface? (1 mark) c) Write a code fragment for a class that implements the ExampleInterface interface. public interface ExampleInterface // Interface method definition void SetValueMethod(int y); Question 2: Code segment for ExampleInterface.

3 Page 3 of 16 COMP Given the code segment in Appendix 1, ObjectVariables1Example, the supplementary Program Listing(s) at the end of this exam paper. Given that Fred has been instantiated, what are the values of: a) Test? b) Val? c) Old? with reference to object Fred. 4. With reference to exception handling in Java, answer the following related questions: a) What does the key word throw enable a program to do and where is it derived from; and b) Write a code fragment for the throw program listing that throws a new exception in the public method named method1. (Note: 2 marks for a concise code fragment that includes a relevant exception string argument that specifies the location of the exception, 1 mark for basic code fragment). public void samplemethod() try method1(); catch ( Exception e ) System.out.println("An exception has occurred: " + e); // The method below is incomplete public static void method1() // Auxiliary code required Question 4: Throw program listing [Code snippet] 5. Java handles interactions with a user by employing event-driven software. Explain what an event is and give an example of an event initiated by a user. [PTO]

4 Page 4 of 16 COMP a) Differentiate between a superclass default constructor super() and a finalize(). In your answer also state when each is normally called; and b) Give examples of typical steps (or processes) a finalizer like finalize() enables a class to undertake. 7. Database servers provide functionality that Java programmers require. State what Database servers actually do, with reference to providing functionality that Java programmers require. (Note: 2 marks for a set of succinct sentences that support the answers, 1 mark for basic explanations). (4 marks) 8. When interacting with a server a client is able to manage (save) client state information. State the three main ways of managing (saving) client state information. 9. Consider the inheritance hierarchy depicted in the diagram below. Two objects are instantiated utilising similar code to that in Appendix 1 of the exam paper. Object variable name Joe is of type ClassC and Fred is of type ClassA. Note: getval; gettest; & getold are class methods. Write a set of code snippets, with appropriate object instantiation, to: a) Access the getval method in ClassC. b) Access the getval method in ClassA. (NOTE: 4 marks for indicating the correct instantiations plus correct method usage, 2 mark if only half the code is specified.) (4 marks) ClassA ClassC Class C Static Vars Local Var Defns Parent Class Class C Methods getval - returns 5 ClassB Class B Static Vars Local Var Defns Parent Class Class B Methods gettest - returns 3 getval - returns 11 Class A Static Vars Non-Static Var Defns Parent Class Class A Methods getval - returns 19 gettest - returns 21 getold - returns 42 Question 9: Class inheritance hierarchy.

5 Page 5 of 16 COMP Given Appendix 2, AccessingBaseMembersExample, Supplementary Program Listing(s) at the end of this exam paper, write the missing code in the class Cylinder such that the method [property] Area() accesses [utilises] the super class Circle properties, to enable it to calculate the area. 11. What does saying that OutputStream is an abstract class mean? What does a typical OutputStream do? Describe briefly the relationship between a File, a FileOutputStream and a BufferedOutputStream. (3 marks) 12. Suppose you had a file containing the text shown below: Artist: Dr. John, Album: Gris-Gris, Price: Artist: Sleepy John Estes, Album: Working Man's Blues, Price: 2.99 Artist: Memphis Minnie, Price: 2.99 Matching each line of this file against the regular expression Artist(.*)Album(.*)Price(.*)\\z would produce a number of 'capture groups'. Show the value of each capture group for each of the lines above. (3 marks) 13. Suppose you had a program that drew pictures like the cafe wall illusion, shown below. Explain briefly the role of the paint method in such a program. (3 marks) [PTO]

6 Page 6 of 16 COMP Describe what the following fragment of Java does, and explain the advantages of using an anonymous inner class here. depthbar = new Scrollbar(Scrollbar.HORIZONTAL, 0, 20, 0, 100); depthbar.addadjustmentlistener( new AdjustmentListener() public void adjustmentvaluechanged(adjustmentevent ae) System,out.println(depthbar.getValue()); ); (3 marks) 15. Consider the following two class definitions: class Link Object value; Link next; Link(Object v, Link n) value = v; next = n; class DLink Object value; DLink prev, next; DLink(Object v, DLink p, DLink n) value = v; prev = p; next = n; Write a method called toxml for writing out entities of type Link as XML, and explain why it is not possible to write a similar method for DLinks. (3 marks)

7 Page 7 of 16 COMP If you use a DOM parser to read a file of XML, you get an object of type Node. Suppose you had written a Link object of the kind defined in Q15 as an XML file. Outline informally what a program for converting a Node to a Link would have to do. (3 marks) 17. Consider the following XML term. <properties> <property> <type>house</type> <address>21 Christchurch Rd</address> </property> </properties> Assuming that you had a Transformer that ignored the white space around the tags, what would the following XSL file produce from this term? <xsl:template match="properties"> Properties for sale or rent <xsl:apply-templates/> </xsl:template> <xsl:template match="property"> <xsl:apply-templates/> </xsl:template> <xsl:template match="type"> </xsl:template> <xsl:template match="address"> <xsl:apply-templates/> </xsl:template> 18. Explain briefly the relationship between the browser on a user s machine, a Tomcat application server and an application program. (4 marks) [PTO]

8 Page 8 of 16 COMP What is the function of the following elements of a web.xml file? <servlet> <servlet-name>upload File</servlet-name> <servlet-class>uploadservlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>upload File</servlet-name> <url-pattern>/upload.do</url-pattern> </servlet-mapping> (3 marks) 20. What would the raw HTML produced by the following fragment of JSP look like, and what would this look like when viewed through a typical browser? We stock the following beers: <% String beers[] = "Young s Special", "Felinfoel Double Dragon"; for(int i=0; i<beers.length; ++i) String s = beers[i]; %> <%= s %> <% %> (3 marks)

9 Page 9 of 16 COMP27010 Section B Answer ONE question from this section. B1. Answer all parts. Reflection as a mechanism is employed in Java. a) Give a detailed and concise description of what reflection actually is. (4 marks) b) Given the reflection code snippet below, write a code snippet that utilises the Field reference balancefield to get the value of the balance. BankAccount1 TestBankAccountField = new BankAccount1(); Class ClassInfo = TestBankAccountField.getClass(); Field balancefield = ClassInfo.getField("balance"); Section B: Question 1: Reflection [Code snippet] c) Given the reflection code snippet above. Write a code snippet that utilises the Field reference balancefield to set the value of the balance to 100. d) What functionality does reflection provide (or support)? (6 marks) e) In Java reflection is supported by a Reflection API that is type-safe and secure. The API supports introspection with respect to classes and objects in the current Java Virtual Machine. State what the API can be used for. (4 marks) f) What are the main get...() methods that the Reflection API provides to assess the primary features of another class? [PTO]

10 Page 10 of 16 COMP27010 B2. Answer all parts. a) Both abstract classes and interfaces are utilised in Java. Compare and contrast abstract classes and interfaces. (4 marks) b) The following Exception handling code extract has some errors. i) Rewrite it correcting all the errors. There are eight errors to be found in the code snippet below. ii) Then state what will be printed by one of the System.out.println( ); statements when the program runs once it has been fully corrected. (5 marks) 1 public TestIndexOutOfRangeException() 2 3 / Test IndexOutOfRangeException 4 int [] TestArray = New int[4]; 5 int ExceptionNo 0; 6 7 try 8 9 int TestInt = TestArray[5; catch(arithmeticexception e) System.out.println("An ArithmeticException. \n") ExceptionNo = 1; catch(java.lang.indexoutofboundsexception ) System.out.println("An IndexOutOfBoundsException. \n"); ExceptionNo = 2; if(exceptionno==0) System.out.println("No Exception has occurred. \n"); Question B2: Exception program listing [Code snippet] (Question B2 continues on the following page)

11 Page 11 of 16 COMP27010 (Question B2 continues from the previous page) c) With reference to the above exception program listing; if line nine in the program were replaced with int a = 3/0;, e.g. int TestInt =...; is replaced with int a = 3/0; then: i) State which of the exceptions would now be thrown. ii) Also, state what type of exception is thrown, and why. iii) Finally, state what will be printed by one of the System.out.println( ); statements when the program runs. (3 marks) d) State what would happen if a catch handler catches an exception but cannot process it. (1 mark) e) Explain what happens to unhandled exceptions. (1 mark) f) If one or more catches are used they may be followed by a finally clause, the finally clause is obeyed in every case. Give examples of when the finally clause is obeyed. (3 marks) g) Write down the basic skeleton of a code snippet that outlines (defines) the correct usage of a finally clause, in a try and catch block. (3 marks) [PTO]

12 Page 12 of 16 COMP27010 Section C Answer ONE question from this section. C1. Consider the program overleaf. This program is supposed to read in a comma-separated file of the form , , , -88 where the first number on each line is an account number and the second line is either a payment into that account and or a withdrawal from it, depending whether it is positive or negative. For each line that it reads it should print out a record like Transaction(account=600078, amount=600) but there are a number of flaws in it. a) What would the program actually do if you gave it a file containing the records above? Define the method(s) that would be needed in order to get it to do what it is supposed to do. (10 marks) b) What would it do with each of the following lines: , 400, , 50 (6 marks) c) What would you have to do to it to make it print error messages when it read these lines and then continued processing the remainder of the input file. (4 marks) (Question C1 continues on the following page)

13 Page 13 of 16 COMP27010 (Question C1 continues from the previous page) import java.io.*; import java.util.*; import java.lang.math.*; public class ReadCSVRevision public static void main(string args[]) new ReadCSVRevision(args); ReadCSVRevision(String args[]) try BufferedReader br = new BufferedReader( new InputStreamReader(new FileInputStream(args[0]))); String s ; while((s = br.readline())!= null) ArrayList list = new ArrayList(); StringTokenizer st = new StringTokenizer(s, ","); while(st.hasmoretokens()) String t = st.nexttoken(); int i = Integer.parseInt(t.trim()); list.add(i); System.out.println(new Transaction(list)); catch(exception e) System.out.println(e); class Transaction int account, value ; Transaction(ArrayList list) account = (Integer) list.get(0); value = (Integer) list.get(1); [PTO]

14 Page 14 of 16 COMP27010 C2. Consider the fragment of XML below. <?xml version="1.0" encoding="utf-8"?> <Personnel> <Employee type="permanent"> <Name>Seagull</Name> <Id>3674</Id> <Age>34</Age> </Employee> <Employee type="contract"> <Name>Robin</Name> <Id>3675</Id> <Age>25</Age> </Employee> <Employee type="permanent"> <Name>Crow</Name> <Id>3676</Id> <Age>28</Age> </Employee> </Personnel> a) Write a DTD that would characterise the data recorded in this file. (8 marks) b) Write an XSL file which would produce the output shown below if viewed through a typical browser. (12 marks) END OF EXAMINATION Appendices follow on 2 pages

15 Page 15 of 16 COMP27010 Appendix 1, ObjectVariables1Example: Supplementary Program Listing(s) //******************************************************************** public class ClassA private int Val = 19; private int Test = 21; private int Old = 42; public ClassA() public int getval() return Val; public int gettest() return Test; public int getold() return Old; //******************************************************************** public class ClassB extends ClassA private int Test = 3; private int Val = 11; public ClassB() public int getval() return Val; public int gettest() return Test; //******************************************************************** public class TestB public TestB() public void samplemethod() ClassB Joe = new ClassB(); ClassB Fred = Joe; int Test = Fred.getTest(); int Val = Fred.getVal(); int Old = Fred.getOld(); //********************************************************************

16 Page 16 of 16 COMP27010 Appendix 2, AccessingBaseMembersExample: //******************************************************************** public class Circle public double radius; public Circle() radius = 0.0; public Circle(double r) radius = r; public double Area() // Area = PI * r^2 return Math.PI * radius * radius; //circumference = PI * diameter or //circumference = PI * (radius * 2) public double Circumference() return Math.PI * radius * 2; //****************************************************************** public class Cylinder extends Circle public double height; public Cylinder() super(); height = 0.0; public Cylinder(double r, double h) super(r); height = h; //area = 2 * (PI * r^2) + (PI * (radius * 2)) + height public double Area() return // missing Code; //********************************************************************

COMP200 - Object Oriented Programming: Test One Duration - 60 minutes

COMP200 - Object Oriented Programming: Test One Duration - 60 minutes Study the following class and answer the questions that follow: package shapes3d; public class Circular3DShape { private double radius;