Information
AI Chat

This is a Premium Document. Some documents on Studocu are Premium. Upgrade to Premium to unlock it.

EXAM November 2011, questions and answers

Course

Java programming (CSC1016S)

174 Documents

Students shared 174 documents in this course

University

University of Cape Town

Academic year: 2011/2012

Uploaded by:

Anonymous Student

This document has been uploaded by a student, just like you, who decided to remain anonymous.

University of Cape Town

Comments

Please sign in or register to post comments.

Related Studylists

Java programming - 2024/11/06 Java programming - 2024/11/06 Java

Preview text

Name: ______________________ Please fill in your Student Number and Name. ______________________ Student Number : __________________________________ Student Number: ______________________ University of Cape Town ~ Department of Computer Science Computer Science 1016S ~ 2011 November Examination ** SOLUTIONS ** Question Max 1 8 2 4 3 8 4 8 5 12 6 10 7 10 8 20 9 20 TOTAL 100 Marks : 100 Time : 180 minutes Mark Moderator Instructions: a) Answer all questions. b) Write your answers in PEN in the spaces provided. c) Show all calculations where applicable. Question 1: Instruction Execution Order [8 marks] (a) How many times does the while loop below execute for each of the different options for line 14? 11 int y = -3, x = 0; 12 while (x &amp;gt; y) 13 { 14 //insert code that alters the condition 15 if (x==11) 16 y=20; 17 x ++; 18 }//How many times did the loop execute? i. Line 14 x+=2; [2] x *=2; [2] x +=5; [2] 4 loops ii. Line 14 infinite iii. Line 14 2 loops (b) Write code to convert the while loop into a for loop. for (;x&amp;gt;y; x++) [2] Question 3 : Accessibility [8 marks] (a) Study this code and answer the questions that follow. Assume that the code is located in the same folder/directory with the Person class from the previous question. package test1; /** * Driver * @author admin */ public class Driver { public static void main(String arg[]) { // instantiate an object called john that // takes no parameter 1 2 3 4 5 System.out(john); System.out(john); System.out(john); } } i. In Driver program, instantiate an object called john that takes no parameter at line #1.[1] Person john = new Person(); ii. Can line #3 be compiled? If yes, what is the output? If not, why not? [1] System.out(john); =&amp;gt; John iii. Can line #4 be compiled? If yes, what is the output? If not, why not? [1] System.out(john); =&amp;gt;False iv. Can line #5 be compiled? If yes, what is the output? If not, why not? [1] System.out(john); =&amp;gt; 1000000 (b) Study this code and answer the questions that follow. Assume that the code is located in the same folder/directory with the Person class from the previous question. package exam; /** * Driver1 * @author admin */ public class Driver1 { 4 public static void main(String arg[]) { // instantiate an object called peter that has name // “Peter” and “Durban” 1 2 3 4 5 System.out(peter); System.out(peter); System.out(peter); } } i. In Driver1 program, instantiate an object called peter that takes “Peter” and “Durban” as its name and address parameters respectively at line #1. [1] Person peter = new Person(&amp;quot;Peter&amp;quot;, &amp;quot;Durban&amp;quot;); ii. Can line #3 be compiled? If yes, what is the output? If not, why not? [1] System.out(peter); =&amp;gt; Peter iii. Can line #4 be compiled? If yes, what is the output? If not, why not? [1] System.out(peter); =&amp;gt; False iv. Can line #5 be compiled? If yes, what is the output? If not, why not? System.out(peter);=&amp;gt; False 5 [1] (c) Briefly state the purpose/effect of each of the statements numbered //1 to //5 above (i. say why it is there or what would happen if it was left out). [5] //1: because default without this is to hide the window on close, not exit //2: allows placement of items on top/bottom/left/right/middle (or: without this they are placed on top of each other so that only 1 thing is visible) //3: this object implements the listener interface to react to this button-press //4: extracts the string on the button (or: to know which button was pressed) //5: window appears on screen, with just the “new” it would be created but not shown 7 Question 5 : OOP [12 marks] (a) Briefly explain each of the following Java terms so that the difference between the terms in each pair is clear: i. super( ) and this( ) [1] call default superclass constructor; call default constructor of this class itself ii. overriding and overloading [1] subclass redefines superclass method while keeping same signature; same class has multiple methods with same name but different signature iii. inheritance and polymorphism [1] when a subclass reuses the variables and methods of its superclass; associating different meanings with the same method name and using late binding (b) What 3 kinds of method are statically bound rather than dynamically bound? constructors, static and final methods (c) Consider the Java program below and answer the questions that follow. public class Result { Student stu; int votes; public Result( ) {votes = 0; stu = null; System.out(&amp;quot;made result&amp;quot;);} public String toString( ) {if (stu != null) return stu + &amp;quot;=&amp;quot; + votes; else return “?=” + votes; } // - - - other code not shown here public static void main (String[ ] args) { System.out(“A”); Result x = new Result( ); System.out(“B”); SRCresult ann = new SRCresult( ); System.out(x); System.out(ann); Result pam = new SRCresult( ); System.out(pam); } } class SRCresult extends Result { String party; public SRCresult( ) {party = &amp;quot;none&amp;quot;; System.out(&amp;quot;made SRCresult&amp;quot;);} public String toString( ) 8 [3] Question 6 : Abstract Data Types [10 marks] (a) The so-called “millennium bug” was a major problem for the software industry in the late 1990s. In numerous application programs and databases, each date was represented by a string of decimal digits: two digits for the day-in-month number, two digits for the month number, and two digits for the year number. For example, 31 December 1999 was represented “311299”, the leading digits “19” of the year number being implicit. Thus there was no means to represent dates after or before the twentieth century. In principle, the solution was simple: What was it? In practice the problem was enormous: why? [3] The solution was to change things so that the year would be represented with 4 four digits instead of two. [2] In practice the problem was complex because it meant changing every program in which the previous format was used. [1] Clear case of when abstraction is useful. [1] (b) What are the obligations of a class that implements a specific interface? [2] To implement an interface, a programmer must do two things. First, the phrase implements interface_name must be included at the start of the class definition. To implement more than one interface, the interface names must be separated by commas. The programmer must then implement all the methods listed in the definition of the interface. (c) Why is it not possible to instantiate a generic class or method as an array or linked list? [2] An array or a linked list is a container. Generic classes can only be instantiated with base types e. Character. (d) Give an example of a design pattern based on the divide and conquer principle to sort an array. [3] sorting patterns based on selecting a splitting value or parameter [1]. Example Quicksort or mergesort – show how divide and conquer technique would work to solve the sorting problem [2] 10 Question 7 : Linear Data Structures [10 marks] (a) Propose a method, based on the divide and conquer principle, to find the value of the smallest element in an array of n numbers. [2] A divide and conquer sorting algorithm that uses a “pivot” as a splitting criteria is a good way of solving this problem [1] The algorithm can recursively split the array into elements that are less than and greater than or equal to the selected pivot. Each recursion will focus on the half of the array that is less than the pivot instead of on the whole array. [1] (b) Give a pseudo-code algorithm or explain how you would apply the selection sort algorithm to order the following array of characters – E X A M P L E Remember that selection sort works by maintaining a sorted left half of the array. So at any point in time all of the elements to the left of the current sort position will be ordered incrementally. [4] Result A E E L M P X. [2] First step compare element in first position with elements in other position. Hold any element, smaller than one in first position, in a temporary variable called “min” and make a note of the position (index) of the element in the array. [1] When the end of the list is reached swap min value with element in position 1. Repeat the procedure for elements starting at position 2. Algorithm terminates when nth element is reached. [1] Algorithm steps on EXAMPLE: Step 1: Comparing E with other elements in array results in swap between A and E to give: AXEMPLE. Step 2: Comparing X with all elements after X results in swap with first E to give AEXMPLE Step 3: Comparison results in swap with last E to give: AEEMPLX Step 4: Comparison between M and other array elements results in swap between L and M to give AEELPMX Step 5: Comparison between P and other elements in array gives : AEELMPX Step 6 and 7: No swaps needed and array is finally sorted. (c) Examine the following piece of code and explain what it does. public class computesomething { private class Node { private char item; private Node next; public Node(char newItem, Node linkValue) { item = newItem; next = linkValue; } } 11 [4] h('O'); h('N'); h(); } } Creates and Inserts elements into a chained hash table of size 5. [2] The result generated is as follows [2]: (H[i] is the chained hash table entry and --&amp;gt; the attached linked list) H[0] --&amp;gt; O --&amp;gt; T --&amp;gt; Y --&amp;gt; E H[1] --&amp;gt; U --&amp;gt; A H[2] --&amp;gt; Q H[3] --&amp;gt; H[4] --&amp;gt; N --&amp;gt;I --&amp;gt; S 13 Question 8 : Ethics, Cyberlaw and Development [20 marks] (a) Carl is an experienced systems designer. He currently works for general purpose software and hardware company on a project for a prominent contractor to the South African Department of Defence. The project involves developing a system that monitors radar signals for incoming missiles and launches missiles to counter the threat when deemed necessary. Carl was initially reluctant but eventually agrees. His thinking was that if he does not do it, someone else will anyway. During his work he develops serious reservations concerning the safety of the system and its ability to make the fine distinction between missiles and small planes. It could retaliate automatically against small planes rather than the intended target of incoming missiles. He expresses this to his project manager who promptly dismisses the claim on the basis that he does not agree with the claim and that the project was already late. i. Carl feels he has a responsibility to do something more. What should his further actions be? [2] He should first approach his immediate superiors, then those above them and so go up the hierarchy in his company. Only if that does not work should he go public and “blow the whistle”. [2] ii. Assume that the project has been declared confidential and that the new proposed South African Protection of Information Bill has been passed. What would the likely consequences be for Carl if he proceeds with public disclosure of the issue in what he believes is the public interest? [4] Under the new protection of information bill he will be jailed if he goes public and he will have no recourse to a “public interest defence” in court. [4] (b) Jeremy Bentham, a Utilitarian philosopher, designed model prison called a “Panopticon”. i. What characterizes Utilitarian philosophy? [2] Everyone should act so as to bring about the greatest amount of happiness for the greatest number of people. Or the good ends justifies the means provided all people are counted equally. Or An action is right if it maximises benefits over costs for all involved, everyone counting equal. [2] ii. What was the underlying principle of human behaviour on which the “Panopticon” worked? [2] When people believe that they are being watched: they behave differently and they think of themselves as observer may think of them [2] iii. In today’s world we have closed circuit TV monitoring of public areas, we have mobile phone monitoring via the Regulation of Interception of Communications and Provision of Communication-Related Information Act (RICA), as well as voluntary visibility of private information on the internet (via blogs, Facebook and Twitter, for example). Discuss the extent that society is now an open prison based on panopticon design. Give arguments for and against. [6] 14 Question 9 : Healthcare Information Management System [20] The South African government has decided that all citizens should have access to their medical records, in keeping with the Promotion of Access to Information Act (2000). • Information about a citizen includes: Name, Gender, Age, ID number, Address. • Each citizen can view his or her information but update only their address. • Medical records include: ID number, date, doctor; along with illness, notes and medicine (this is if the record is from a doctor) or injection, date, weight and pulse (this is if the record is from a clinic). • Each medical record belongs to a particular citizen who can be identified by ID number and a citizen can have any number of records. • The system can store and retrieve all information about the citizen. It can create a new medical record corresponding to each citizen. The medical record could either be a record from a doctor or a record from a clinic. • Given a correct ID number, a citizen can print their medical records. Assume that all data is stored in a suitable data structure in memory while the program is running and then answer the following questions on this data structure. Hint: Read ALL the questions in this section before you begin to answer any of them as the design of your solution must address all the issues noted. (a) Draw a UML class diagram to illustrate all classes of the system and the relationships among them. In particular, i. Identify the classes (there are 3 classes). [1] ii. Draw a full class diagram for only one class. [2] iii. Draw the relationship among the 3 classes. [2] (b) Discuss the classes and the relationships between them in terms of satisfying the requirements of professionally produced software according to accepted codes of practice? [5] The answer depends on an appreciation of the issues covered in the CSSA or BCS code of practice. We do not expect students to memorize these but they do need to be able to recognize important issues. Basically a single mark will be given for every correct statement. Given the slant of the question most would fall under the headings of Privacy, Security and Integrity. But other possibilities are not excluded. So as an example a good answer would include the following (Max 5!): Medical records contain sensitive personal information so a number of the classes included in the design deal with privacy, security and data integrity concerns [1]. The system will also comply with relevant legislation on storing personal data.[1] The risks have been evaluated [1] and the database has to be stored on a secure server. [1] We included an encrypted password class to ensure security [1]. Repeated failed log-in attempts are traced via the “failed” attribute in the database record that will cause the record to be locked after several failed attempts to access a person’s record [1]. 16 The log files for all transaction are design to allow all breaches of be traced [1]. When the address is changed a notification will be sent (/emailed) to the person concerned [1]. A privacy statement is included in the class “WebInfo” and can be updated by the system operator and users will be encouraged to keep their passwords safe [1]. And also: design statements that refer to reusability, testing, maintainability, etc will all gain marks. (c) Write two algorithms (in pseudocode or Java): one to insert a new citizen record with an associated medical record, and one to search for the records of persons based on their ID numbers. [10] Some variation of a linked list or a hash table with collision resolution by chaining. 5 marks per algorithm/method. 17

Multiple Choice

Multiple Choice

Was this document helpful?

Premium

This is a Premium Document. Some documents on Studocu are Premium. Upgrade to Premium to unlock it.