SCHOOL OF COMPUTING, ENGINEERING AND MATHEMATICS SEMESTER 2 EXAMINATIONS 2013/2014 CI101/CI101H. Programming

Transcription

1 s SCHOOL OF COMPUTING, ENGINEERING AND MATHEMATICS SEMESTER 2 EXAMINATIONS 2013/2014 CI101/CI101H Programming Time allowed: THREE hours Answer: ALL questions Items permitted: Items supplied: There is no restriction on the paper-based items or items on a USB flash drive that the student may take into the examination. None CI101_SEM2_2013/2014 Page 1 of 24 Printing date: 20/10/2014

2 Section A Section A carries 50 marks in total. Use the application provided to record the answer for each multiple choice question (Question 1 Question 20) in section A of this exam paper. Remember to fill in your student number in the box provided for this (Highlighted initially with a reddish background ) before exiting from the application. Each question in Section A is worth 2.5 marks. Section A carries 50 marks in total. There is no penalty for answering a question wrongly. Question 1 class Main public static void main( String args[] ) System.out.printf( "%s%s%s\n", "hello", " ", "world" ); When the above class Main is executed as a Java application it will print: Hello world %s %s\n Hello world %s %s\n Hello world CI101_SEM2_2013/2014 Page 2 of 24 Printing date: 20/10/2014

3 Question 2 class Main public static void main( String args[] ) int totalhours = 36; int days = totalhours / 24; int hours = totalhours % 24; System.out.println( totalhours + " hours is equal to " + days + "." + ((hours*10)/24) + " days(s)" ); When the above class Main is executed as a Java application it will print: 36 hours is equal to 1.0 days(s) 36 hours is equal to 1.5 days(s) 36 hours is equal to 2.0 days(s) 36 hours is equal to 2.5 days(s) CI101_SEM2_2013/2014 Page 3 of 24 Printing date: 20/10/2014

4 Question 3 class Main public static void main( String args[] ) if ( false && true ) System.out.println("OK"); if ( false true ) System.out.println("OK"); if ( false true ) System.out.println("OK"); if ( ( false == false ) (false == true) ) System.out.println("OK"); if ( true && (! ( 1!= 1) ) ) System.out.println("OK"); if ( 10 < 20 && 'a' > 'b' ) System.out.println("OK"); When the above class Main is executed as a Java application it will print: OK (will be printed) once. OK (will be printed) two times. OK (will be printed) three times. OK (will be printed) four times. CI101_SEM2_2013/2014 Page 4 of 24 Printing date: 20/10/2014

5 Question 4 class Main public static void main( String args[] ) double value = 0.0; value = (double) ( 5 / 2 ); System.out.printf( "%8.1f\n", value ); value = 5 / ( int) 2.0; System.out.printf( "%8.1f\n", value ); value = (double) (5.0 / 2); System.out.printf( "%8.1f\n", value ); value = (int) (5.0 / 2.0); System.out.printf( "%8.1f\n", value ); value = (short) (5.0 / 2.0); System.out.printf( "%8.1f\n", value ); When the above class Main is executed as a Java application it will print: 2.0 will be printed two times. 2.0 will be printed three times. 2.0 will be printed four times. 2.5 will not be printed. CI101_SEM2_2013/2014 Page 5 of 24 Printing date: 20/10/2014

6 Question 5 class Main public static void main( String args[] ) for ( int i=10; i>=1; i-- ) if ( i > 5 && i < 4 ) System.out.println( "Interesting" ); When the above class Main is executed as a Java application it will print: Interesting will not be printed. Interesting will be printed once. Interesting will be printed two times. Interesting will be printed three times. Question 6 class Main public static void main( String args[] ) int numbers[] = 1, 2, 3, 4, 5 ; System.out.print( numbers[ numbers[ 3 ] ] ); numbers[2] = numbers[ numbers.length-3 ]; System.out.println( numbers[ 2 ] ); When the above class Main is executed as a Java application it will print: CI101_SEM2_2013/2014 Page 6 of 24 Printing date: 20/10/2014

7 Question 7 class Box private String stored = null; public Box( String s ) stored = s; public String stored() return stored; class Main public static void main( String args[] ) Box b1 = new Box( "ents" ); Box b2 = new Box( "pres" ); Box b3 = new Box( "cont" ); b2 = b3; System.out.println( b2.stored() + b1.stored() ); When the above class Main is executed as a Java application it will print: prespres presents contents contcont CI101_SEM2_2013/2014 Page 7 of 24 Printing date: 20/10/2014

8 Question 8 import java.util.arraylist; class Person private String name = "No one"; private int score = 0; public Person( String name, int score ) this.name = name; this.score = score; public String getname() return name; public int getscore() return score; class Main ArrayList<Person> players = new ArrayList<Person>(); players.add( new Person( "John", 34 ) ); players.add( new Person( "Janet", 23 ) ); players.add( new Person( "Ann", 45 ) ); players.add( new Person( "Nathan", 47 ) ); int winscore = players.get(0).getscore(); String winname = players.get(0).getname(); for( Person cur : players ) if ( winscore > cur.getscore() ) winname = cur.getname(); winscore= cur.getscore(); System.out.println( "Winner is " + winname ); When the above class Main is executed as a Java application it will print: Winner is Ann Winner is Janet Winner is John Winner is Nathan CI101_SEM2_2013/2014 Page 8 of 24 Printing date: 20/10/2014

9 Question 9 class Main public static void main( String args[] ) int numbers[] = 0, 1, 0, 1, 1 ; int result = 0; for ( int i=0; i < numbers.length; i++ ) result = result * 2 + numbers[ i ]; System.out.println( result ); When the above class Main is executed as a Java application it will print: CI101_SEM2_2013/2014 Page 9 of 24 Printing date: 20/10/2014

10 Question 10 class Main public static void main( String args[] ) boolean va[] = true, true, false, false ; boolean vb[] = true, false, true, false ; System.out.println( "A B (A B) & B " ); for( int i=0; i<va.length; i++ ) System.out.printf( "%s %s %s\n", convert( va[i] ), convert( vb[i] ), convert( (va[i] vb[i] ) && vb[i] ) ); public static String convert( boolean value ) return value? "T" : "F"; When the above class Main is executed as a Java application it will print: A B (A B) & B F F F F T T T F F T T T A B (A B) & B F F F F T T T F T T T T A B (A B) & B T T T T F T F T T F F F A B (A B) & B T T T T F F F T T F F F CI101_SEM2_2013/2014 Page 10 of 24 Printing date: 20/10/2014

11 Question 11 Which of the following statements about Java is true? An instance of a double will always hold any calculated value exactly such as the result of 1.0/3.0 or * * After executing the statement double d=2.3; the variable d may be converted into an int with the Java statement int a = d; An instance of a boolean may only take the values true or false. The operator += may only be used between instances of an int or double. Question 12 Which of the following statements about Java is true? An if statement must have an else part. A case statement must always have a default case label. The body of a while statement will always be executed at least once. If the following variables a, b and c have all been declared as an instance of an int. Then the following assignment statement is valid: int result = a = b = c = 2; Question 13 Which of the following statements about Java is true? A valid index to collection which is an instance of an ArrayList must be a whole number in the range 0 to collection.size()-1;. A valid key to access information stored in an instance of a HashMap must only be an instance of an int or an instance of the class String. You can decrease the number of accessible elements in an array in Java by changing the contents of it s field length. An instance of an ArrayList numbers may be used to store int s by using the declaration: ArrayList<int> numbers = new ArrayList<int>();. CI101_SEM2_2013/2014 Page 11 of 24 Printing date: 20/10/2014

12 Question 14 Which of the following statements about Java is true? All of the following are primitive types in Java: int, double, boolean, String. An instance of a String may only have its contents changed if the resultant String would be less than or equal to the original String's length. If you examine a character in a String using the method charat then a new instance of the string will be created on each method invocation. message.tolowercase(); The above Java statement will not convert the characters in the String message to lower case. Question 15 Which of the following statements about Java is true? A constructor in a class is called just before the objects storage is released by the garbage collector. The last code line of a constructor must be return this; which will return the current state of the object. A constructor's signature must not have a return type. You may only define 1 (one) constructor in a class. CI101_SEM2_2013/2014 Page 12 of 24 Printing date: 20/10/2014

13 Question 16 Which of the following statements about Java is true? An object is also an instance of a primitive type. A message is invoked when a method is sent to an object An instance of a class is an object. The primitive type int is an instance of the class Integer. Question 17 Which of the following statements about Java is true? Java is "write once run anywhere" because it is compiled into native machine code. Java is "write once run anywhere" because it is not compiled into a bytecode but source interpreted and hence can be run on any machine. Java is "write once run anywhere" because there is now only 1 (one) computer architecture used by all computers. Java is "write once run anywhere" because Java is compiled into a bytecode that may be executed on many machines. CI101_SEM2_2013/2014 Page 13 of 24 Printing date: 20/10/2014

14 Question 18 Which of the following statements about Java is true? It is better to use in Java an array rather than an ArrayList to store data as an ArrayList may not increase the number of objects stored. A TreeMap stores [key, data] pairs of objects. The key is then used to retrieve the stored data. An ArrayList may be used as a direct substitute for a HashTree. In general there will be no performance gain in using a HashMap rather than a TreeMap to store and retrieve data items using a key. Question 19 Which of the following statements about Java is true? To compare the contents of any object the equality operator == must be used. An object which is an instance of the String class is mutable. An object which is an instance of the String class is immutable. An instance of the String class is not an object. Question 20 Which of the following statements about Java is true? In a large program it is better to avoid the use of classes as there use often involves the creation of extra code to call methods which just access instance variables in the many different objects that will exist in the program. A TreeMap should not be used if it is required to process the stored data in key order. The program java is used to compile a Java program. The convention is that the name of mutable instance variable starts with a lower case letter. CI101_SEM2_2013/2014 Page 14 of 24 Printing date: 20/10/2014

15 Section B Section B carries 50 marks Marks Brief A Java application has been written to produce an inventory of items. In this application single items are input and at the end of the input a list of items in the inventory will be produced. If however, an item is already in the inventory, then rather than record a new entry the count of the number of examples of this item is increased by 1. If the inventory is full and a new item that is not already in the inventory is attempted to be added then the error message Error full: Inventory so far Is written followed by the contents of the inventory. The maximum size of the inventory is set to 5 items to facilitate testing. This value should not be changed. Unfortunately, the application contains (in total 5 individual errors) syntax, semantic and run-time logical errors. A BlueJ project for this application named 2.1 is in the folder ci101.exam at the top level on the h: drive. Using BlueJ correct these errors, so that the application produces the expected result. Remember do not re-write the program, but correct the errors in the program. CI101_SEM2_2013/2014 Page 15 of 24 Printing date: 20/10/2014

16 Example Input Example input data usb cable cpu disk drive ssd disk cpu cooler cpu one too many items END Commentary ** inventory full 6 th item ** Terminator Expected output Error full: Inventory so far usb cable [ 1] cpu [ 2] disk drive [ 1] ssd disk [ 1] cpu cooler [ 1] Example Input Example input data usb cable cpu disk drive ssd disk disk drive ssd disk ssd disk END Commentary Terminator Expected output usb cable [ 1] cpu [ 1] disk drive [ 2] ssd disk [ 3] CI101_SEM2_2013/2014 Page 16 of 24 Printing date: 20/10/2014

17 Special instructions Put as a comment at the top of your program your student number. Note: o Arrays are used to store the items in the inventory o The inventory is not sorted; items are simply listed in the order that the first occurrence of an item is encountered in the input. o The items to be input to the inventory are terminated with an item named END. Remember any line printed that contains a # character will not be considered as part of your answer. This is so that you can write out a meaningful prompt for any data (containing a # character) and this whole line of text will be ignored in the comparison of your answer. The program A printed copy of the Java application for question 2.1 (that contains the errors mentioned above) is on the following page. CI101_SEM2_2013/2014 Page 17 of 24 Printing date: 20/10/2014

18 class Main public static void main( String args[] ) Inventory list = Inventory(); boolean ok = true; System.out.print("#Enter item name : " ); String item = BIO.getString(); while (! item.equals( "END" ) && ok ) ok = list.add( item ); if (!ok ) break System.out.print("#Enter item name : " ); item = BIO.getString(); if ( ok ) System.out.println("Error full: Inventory so far" ); System.out.println( list.asstring() ); classs Inventory private final static int MAX = 5; private int nextfree = 0; private String item[] = new String[MAX]; private int howmany[] = new int[max]; public boolean add( String anitem ) // Find if item already exists for ( int i=0; i<nextfree; i++) if ( item[i].equals( anitem ) ) howmany[i]++; return true; if ( nextfree < MAX ) // Add a new item to the inventory item[nextfree] = anitem; howmany[nextfree++] = 0; return true; return false; public String asstring() String result = ""; for ( int i=0; i<nextfree; i++ ) result += String.format("%-16s [%4d]\n", item[i], howmany[i] ); return result; CI101_SEM2_2013/2014 Page 18 of 24 Printing date: 20/10/2014

19 Marks Brief A Java application has been written to calculate the mean or average mark for a group of students taking a module. The data to the program consists of the students name followed by their mark for this module. The data is terminated with a student name of END. The application in Java has been written using 3 classes. The class Student An instance of which is used to store the name and mark for an individual student taking a module. The class Module An instance of which is used to hold the students taking the module with a method to calculate the average mark for students taking the module. The class Main Is used to read in data pairs consisting of the students name and their mark for the module and store the data in an instance of a module. Unfortunately, the application contains (in total 5 individual errors) syntax, semantic and run-time logical errors. A BlueJ project for this application named 2.2 is in the folder ci101.exam at the top level on the h: drive. Using BlueJ correct these errors, so that the application produces the expected result. Remember do not re-write the program, but correct the errors in the program. CI101_SEM2_2013/2014 Page 19 of 24 Printing date: 20/10/2014

20 Example Input Example input data Alice 68 Beatrix 70 Catherine 72 Deborah 66 Eliza 64 END Commentary Student name Module mark out of 100 Student name Module mark out of 100 Student name Module mark out of 100 Student name Module mark out of 100 Student name Module mark out of 100 Terminator Expected output Average mark is CI101_SEM2_2013/2014 Page 20 of 24 Printing date: 20/10/2014

21 Special instructions Put as a comment at the top of your program your student number. Note: o The data is terminated by entering a student with the name END. o The Module mark will always be a number in the range: o There will always be at least one person taking a module. Remember any line printed that contains a # character will not be considered as part of your answer. This is so that you can write out a meaningful prompt for any data (containing a # character) and this whole line of text will be ignored in the comparison of your answer. The program A printed copy of the Java application for question 2.2 (that contains the errors mentioned above) is on the following page. CI101_SEM2_2013/2014 Page 21 of 24 Printing date: 20/10/2014

22 import java.util.arraylist; class Student private String thename = "" private int themark = 0; public Student( String name, int mark ) thename = name; themark = mark; public int getname() return thename; public int getmark() return themark; class Module ArrayList<Student> module = new ArrayList<Student>(); public void add( String name, int mark ) module.add( new Student( name, mark ) ); public double mean() double total = 0.0; for ( Student student: module ) total += student.getmark(); return total / 4; class Main public static void main( String args[] ) Module module = new Module(); System.out.print("#Enter student name : " ); String name = BIO.getString(); while (! name.equals("stop") ) System.out.print("#Enter module mark : " ); int mark = BIO.getInt(); module.add( mark, name ); System.out.print("#Enter student name : " ); name = BIO.getString(); System.out.printf("Average mark is %6.2f\n", module.mean() ); CI101_SEM2_2013/2014 Page 22 of 24 Printing date: 20/10/2014

23 Marks Brief Write a Java application that converts numbers in Arabic number format to numbers in Roman number format. In "Roman number" format the letters (I=1, V=5, X=10, L=50, C=100, D=500 and M=1000) are used to express a number. Roman numbers are formed by combining these symbols together and adding the values. So II is two ones, i.e. 2, and XIII is a ten and three ones, i.e. 13. There is no zero in this system, so 207, for example, is CCVII, using the symbols for two hundreds, a five and two ones is MLXVI, one thousand, fifty and ten, a five and a one. Symbols are placed from left to right in order of value, starting with the largest. However, in a few cases to avoid four characters being repeated in succession (such as IIII or XXXX) these can be reduced using subtractive notation as follows: the numeral I can be placed before V and X to make 4 units (IV) and 9 units (IX) respectively X can be placed before L and C to make 40 (XL) and 90 (XC) respectively C can be placed before D and M to make 400 (CD) and 900 (CM) according to the same pattern An example using the above rules would be 1904: this is composed of 1 (one thousand), 9 (nine hundreds), 0 (zero tens), and 4 (four units). To write the Roman numeral, each of the nonzero digits should be treated separately. Thus 1,000 = M, 900 = CM, and 4 = IV. Therefore, 1904 is MCMIV. Modified from the article in Wikipedia on Roman numbers. Example input data Commentary Example Input Add together MM X IV Add together M CM XX III Add together C XC IX Expected output 2014 as a roman number is MMXIV 1923 as a roman number is MCMXXIII 199 as a roman number is CXCIX CI101_SEM2_2013/2014 Page 23 of 24 Printing date: 20/10/2014

24 Special instructions A BlueJ project for this application named 2.3 is in the folder ci101.exam at the top level on the h: drive. Using this BlueJ project construct your answer. The program will be run by invoking the method main in the class Main. Put as a comment at the top of your program your student number. Put as a comment at the top of your program a comment that describes how your program converts a number into a Roman number. Note: That the terminator is a line containing only the number 0. Assume that the number to be converted is in the range The roman number produced will be in upper case letters. Remember any line printed that contains a # character will not be considered as part of your answer. This is so that you can write out a meaningful prompt for any data (containing a # character) and this line of text will be ignored in the comparison of your answer. CI101_SEM2_2013/2014 Page 24 of 24 Printing date: 20/10/2014