In the following description the h: drive is used to indicate the directory in which during the actual ci101 exam the files used will reside.

Transcription

1 Important In the following description the h: drive is used to indicate the directory in which during the actual ci101 exam the files used will reside. However, if you are trying the exam system out yourself using the files from the web site then you will need to put these files in a different location. Suggest your own shared workspace and modify the instructions below to reflect the new location. See also section 5 of this document. M A Smith University of Brighton December 6, 2016 Page 1

2 Important information As during the exam you do not have access to the internet a copy of the lecture notes for CI101 is on the p: drive at: p:\ci101.java\ci101.html 1. At the exam Open the folder Applications -> Computing then double click on the shortcut Cygwin64 Terminal and then in the terminal window type the following lines. (Ignore any error messages you initial see in the terminal window.) Remember to press the return key after entering each line. cd h: cd ci101.exam_place-number Note Replace place-number by your actual place number. At any point in typing ci101.exam_place-number You can press the tab key and the bash shell will expand what you have typed to match a single directory in the current directory. M A Smith University of Brighton December 6, 2016 Page 1

3 Now at the command prompt type: sh menu and the following text menu will be displayed. mct - Run Multiple choice data entry program Check the answer to Check the answer to Check the answer to 2.3 exit - Exit from the menu check - Check the system is ok Which option : Options that can be selected: mct Run the Multiple choice data entry program. Remember to save and exit before selecting another option. 2.1 Run a check on your solution to Run a check on your solution to Run a check on your solution to 2.3 check Check that the exam system is working ok. M A Smith University of Brighton December 6, 2016 Page 2

4 Use the BlueJ project at: h:\ci101.exam_place-number\2.1 to modify/construct and debug your program. Remember to include your student number in a comment at the top of your Java program. For the other programs 2.2 & 2.3 replace 2.1 with 2.2 or 2.3 respectively to use the appropriate BlueJ project. When your program passes the 'test' leave the file(s) that you have created/ modified in BlueJ alone. These will be collected after the exam. M A Smith University of Brighton December 6, 2016 Page 3

5 Summary of BIO Static method call BIO.getInt() BIO.getDouble() BIO.getString() BIO.eof() Description Read a line and return as an int the number that is contained within the line. If the number is malformed then return 0. Read a line and return as a double the number that is contained within the line. If the number is malformed then return 0.0. Read a line and return as an instance of a String the characters that are contained within the line. Returns true if the end of the input has been reached otherwise false. If during a read operation the end of input is detected normally a warning message will be printed and the program will terminate. M A Smith University of Brighton December 6, 2016 Page 4

6 4. Overview The CI101 exam is composed of 20 Multiple choice questions worth (50%) Enter your answers to the multiple choice questions using a Java application 3 Java programs to modify/write worth (50%) You will need to write and test each program using BlueJ. Then check your answer using a local shell script. Note: A copy of your program is made with the following source changes: BIO. is changed to BIOX. public class Main is changed to class Main It is the copy that is compiled and run. CI101 course at: Remember: You can use the computer for the whole of the 3 hours of the exam. M A Smith University of Brighton December 6, 2016 Page 5

7 5. Trying this out The following pages contain exercises for you to try. If these were exam questions, then to develop these programs you would need to set-up in an appropriate pool room the following environment. At: which is a zip file that contains files to unzip to your networked storage. Warning this will create files in a top level directory called ci101.exam_10. So if you already have a directory called this please rename your directory. Now follow the instructions in page 1 & 2 You will not be able to do this at 'home' unless you install the cygwin environment. The environment must contain the commands: cat, cut, diff, echo, grep, head, sed, wc, [java & javac (Oracle version)] Best to try this out in an appropirate pool room at the University. M A Smith University of Brighton December 6, 2016 Page 6

8 Example multiple choice questions Remember there is no penalty for answering a question wrongly Q1 When the program below is run class Main public static void main( String args[] ) System.out.printf( "%s world\n", "hello" ); then the program would print: a) %s world hello b) world hello c) hello world d) A runtime error message Q2 When the program below is run class Main public static void main( String args[] ) int a = 0; // First int b = 1; while( a < 3 ) int tmp = a; // Second a = b; b = tmp + b; System.out.println( a ); // First <- Second // Second = Old First + Second it would print: a) 0 b) 1 c) 2 d) 3 M A Smith University of Brighton December 6, 2016 Page 7

9 Q3 When the program below is run class Main public static void main( String args[] ) int sum = 0; for( int i=0; i<3; i++ ) if ( i == 1 i == 3 i == 5 ) sum++; System.out.println( sum ); it would print: a) 0 b) 1 c) 2 d) 3 M A Smith University of Brighton December 6, 2016 Page 8

10 Q4 When the program below is run class Main public static void main( String args[] ) String s = "Hello world"; int count = 0; for ( int i=0; i<s.length()-1; i++ ) if ( s.charat(i) == s.charat(i+1) ) count++; System.out.println( count ); it would print: a) 0 b) 1 c) 2 d) 10 Q5 When the program below is run class Main public static void main( String args[] ) String s1 = "words"; String s2 = ""; for ( int index=0; index<s1.length()-3; index++ ) s2 = s2 + s1.charat( index ); System.out.println( s2 ); it would print: a) ds b) wo c) oo d) A runtime error message M A Smith University of Brighton December 6, 2016 Page 9

11 Q6 When the program below is run class Main public static void main( String args[] ) int numbers[] = 1, 1, 1, 1, 1, 1, 0, 1 ; int sum = 1; for ( int i=1; i<numbers.length; i++ ) sum = sum + numbers[i]; System.out.println( sum ); it would print: a) 0 b) 7 c) 8 d) 9 Q7 When the program below is run class Main public static void main( String args[] ) System.out.println( mystery( 3, 2 ) ); public static int mystery( int a, int b ) if ( b == 0 ) return a; else return mystery( a+1, b-1 ); it would print: a) 4 b) 5 c) 6 d) 7 M A Smith University of Brighton December 6, 2016 Page 10

12 Q8 Which of the following statements will not compile a) int a = ; b) int a = 36.1; c) int a = "Hello".length(); d) double d = 2; Q9 Which of the following statements is false a) An instance of an int will always occupy the same number of bytes. b) A class must always have at least one constructor provided by the implementor of a class. c) An instance of a class is an object. d) Two methods may have the same name provided there parameters differ. Q10 Which of the following statements is true Q11 a) A Java program may only be run on the machine on which it is compiled on. b) int Java = 2.1; Is a valid Java statement. c) Two methods in the same class with different signatures may have the same name. d) Instance variables must be declared before any methods in a class. Which of the following statements is true a) An instance of the class String is mutable (may be changed). Thus name.replace('.','+') will convert all.'s in name to a +. b) Arrays in Java always start at element 1. c) You should not compare instances of the string class using ==. d) If you wish to hold a value exactly you should use an instance of a double. M A Smith University of Brighton December 6, 2016 Page 11

13 Q12 Which of the following statements is true a) An instance of an int is the same size (in bytes) as an instance of a double. b) The number of elements in the int array numbers is delivered by the expression numbers.length(). c) The code fragment: String s = "Hello world"; System.out.println(s.charAt(0)-'H'); will print h. d) In the statement: Sytem.out.println("Hello"); out is an object. Q13 Which of the following statements is true a) int a = 1+/*2+3*/4; Is not a valid declaration. b) int a = 0123 >>> 2; Is not a valid declaration. c) String s = String.format("%s",""); Will put a string of length 2 in s. d) All of the above statements are false. M A Smith University of Brighton December 6, 2016 Page 12

14 Q14 When of the following statements is true a) String s = "Hello"; Is not a valid declaration. b) String s = new String("Hello"); Is not a valid declaration. c) String s = "Hello".length(); Is not a valid declaration. d) All of the above statements are false. Q15 The following statement "Write once, run anywhere" refers in Java to: a) The fact that as the Java system is available on every computer ever built, a program can be run everywhere. b) The fact that Java is never compiled, but always source interpreted and hence will run on any machine. c) The fact that Java is compiled to a bytecode and an interpreter or just in time compiler is available on many machines to 'run' the program. d) All of the above. M A Smith University of Brighton December 6, 2016 Page 13

15 Q16 class Account private double thebalance = 0.00; //Balance of account private double theoverdraft = 0.00; //Overdraft public double getbalance() return thebalance; public void deposit( final double money ) thebalance = thebalance + money; In the above code, which statement below is false a) thebalance is an instance variable b) theoverdraft may not be accessed from outside of the class Account. c) the method getbalance returns an instance of a double. d) final indicates that in the method deposit the formal parameter money may be modified. M A Smith University of Brighton December 6, 2016 Page 14

16 Q17 Using the class in Q16 with the code fragment below: Account mike = new Account(); Account copy = mike; mike.deposit(100.00); System.out.println("%10.2f\n", mike.getbalance() ); System.out.println("%10.2f\n", copy.getbalance() ); which statement below is true a) mike is an instance of a double. b) mike & copy are of different types. c) The two numbers that would be printed will be the same. d) All of the above statements are true. Not covered in class directly, though you may wish to try Q18 Which of the following statements is true a) Map<String, String> amap = new Map<>(); is not a valid declaration. b) Integer a = 2; Is not a valid declaration. c) double res = 2.0 / 0.0; Will cause a run-time error; d) All of the above statements are false. M A Smith University of Brighton December 6, 2016 Page 15

17 2.1 Warning not the exam question / 15 Marks Brief A Java application has been written to read in a series of numbers representing the size of a side of a 'square'. The data is terminated with a negative number. The application prints for each number a square outlined in *'s with an interior of the characters.+ (repeating). The square will always be an odd number of units in size. If the input value is even, the message " Size must be odd: try again" will be printed Example Input Expected output from above input A Java application has been written but unfortunately it contains a few syntax, semantic and logical errors. Correct these errors. A BlueJ project for this application is in the folder cu101.exam_10 at the top level of the h: drive: Using BlueJ correct the application so that the correct results are printed. Example input data Commentary 7 Size of 'square' 5-1 ******* *.+.+.* *.+.+.* *.+.+.* *.+.+.* *.+.+.* ******* ***** *.+.* *.+.* *.+.* ***** M A Smith University of Brighton December 6, 2016 Page 16

18 Special instructions Remember any line printed that contains a # will not be considered as part of your answer. This is so that you can write out a meaningful prompt (containing a # character) for any data required and this line of text will be ignored in the comparison of your answer. Remember that you have most of the answer. M A Smith University of Brighton December 6, 2016 Page 17

19 class Main public static void main( String args[] ) boolean process = false; while ( process ) System.out.print("#Enter size of box [<0 to exit]: ") int sq = BIO.getInt(); if ( sq < 0 ) process = false; else if ( sq%2 == 0 ) System.out.println( "Size must be odd: try again" ); else printbox( sq ); private static void printbox( int size ) for ( int row=1; row<=size; row++ ) for ( int col=1; col<=size; col++ ) if ( row == 1 row == size ) System.out.print("*"); else if ( col == 1 && col == size ) System.out.print( "*" ); else if ( col%2 == 0 ) System.out.print( " " ); else System.out.print( "+" ); System.out.print(); M A Smith University of Brighton December 6, 2016 Page 18

20 2.2 Warning not the exam question / 15 Marks Brief A Java application has been written to encrypt or decrypt a line of text using a Caesar cipher (attributed to Julius Caesar). In this a key is used to shift a plain text letter by key places up/down. For example if the key was 3, then abc becomes def. Each letter is replaced by the corresponding letter 3 places on. For example, a d, be, cf and zc [Cycle round to the start if go beyond z] To decrypt a message, the process is reversed, (key=-3) so d a and c would become z (each letter is shifted key places down, cycle round to the end if go below a. The program takes as input the key (how many places to shift each letter) followed by a series of messages to be encrypted/ decrypted terminated by the string END. All characters that are not alphabetic are ignored by being converted to a space and all characters are treated as being lower case. A Java application has been written but unfortunately it contains a few syntax, semantic and logical errors. Correct these errors. A BlueJ project for this application is in the folder cu101.exam_10 at the top level of the h: drive: Using BlueJ correct the application so that the correct results are printed. M A Smith University of Brighton December 6, 2016 Page 19

21 Example Input Encrypt Example input data 3 abcdefghijklmnopqrstuvwxyz a message in plain text END Commentary Shift by text text End of input Expected output from above input Original text: abcdefghijklmnopqrstuvwxyz En/Decrypted : defghijklmnopqrstuvwxyzabc Original text: a message in plain text En/Decrypted : d phvvdjh lq sodlq whaw Example Input Decrypt -3 defghijklmnopqrstuvwxyzabc d phvvdjh lq sodlq whaw END Shift by text text End of input Expected output from above input Original text: defghijklmnopqrstuvwxyzabc En/Decrypted : abcdefghijklmnopqrstuvwxyz Original text: d phvvdjh lq sodlq whaw En/Decrypted : a message in plain text Special instructions Remember any line printed that contains a # will not be considered as part of your answer. This is so that you can write out a meaningful prompt (containing a # character) for any data required and this line of text will be ignored in the comparison of your answer. Remember that you have most of the answer. M A Smith University of Brighton December 6, 2016 Page 20

22 class Main public static void main( String args[] ) System.out.print("#Enter key : " ); int key = BIO.getInt(); EncryptDecrypt ed = new EncryptDecrypt() ed.setkey( keys ); System.out.print("#Enter line of text : " ); String line = BIO.getString(); while (! line.== "END" ) System.out.println("Original text: " + line ); System.out.println("En/Decrypted : " + ed.process( line ) ); System.out.print("#Enter line of text : " ); line = BIO.getString(); class EncryptDecrypt private int key = 0; private String text = ""; public void setkey( int k ) key = k; public int process( String line ) line = line.tolowercase(); String res = ""; for ( int i=0; i<=line.length(); i++ ) char c = line.charat(i); //Get ith char if ( c >= 'a' && c <= 'z' ) int chn = c-'a'; //Letter to number 0-25 chn = chn + key; //move on key positions if ( chn >= 0 ) chn = chn % 26; //Forward else chn = 26 + chn; //Reverse c = (char) (chn+'a'); //Back to letter res += c; //Append else res += ' '; //Append space return res; M A Smith University of Brighton December 6, 2016 Page 21

23 2.3 Warning not the exam question / 20 Marks Brief Write a program to input lines of text that contain an English description of a number such as: six thousand nine hundred and sixty seven and to print out the number as a decimal number. The words used will be: one, two, three, four. five, six, seven, eight, nine, ten, twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety, hundred, thousand, and The input will be terminated with a line that has only the word END in upper case. Example Input Expected output from above input Special instructions Example input data Commentary two Line 1 thousand Line 2 five Line 3 hundred Line 4 and Line 5 ninety Line 6 END END [two thousand five hundred and ninety] = 2590 Remember to submit the whole application which must have the class name Main. Remember any line printed that contains a # 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. If the String variable name holds the character string END then name.equals("end") will return true. Hint The definition of a number is deliberately vague, higher marks will be awarded for working within the inherent ambiguity M A Smith University of Brighton December 6, 2016 Page 22

24 1. Alternative way of running the exam system From the start (icon bottom left corner) select the search dialogue box replacing 'search programs and files' with cygwin. Select 'cygwin bash shell' and then at the newly created windows command prompt type the following two lines. Remember to press the return key after each line. cd h:/ci101.exam_place-number sh system.sh Note The use of / instead of \ in the path place-number is your place number 2. Entering the Multiple choice questions From the start (icon bottom left corner) select the search dialogue box replacing 'search programs and files' with cygwin. Select 'cygwin bash shell' and then at the newly created windows command prompt type: cd h:/ci101.exam_place-number sh mct.sh Note The use of/ instead of \ in the path The line cd h:/ci101.exam_place-number may be omitted if already in this directory. M A Smith University of Brighton December 6, 2016 Page 23

25 3. Completing a Java program In the following instructions the assumption is that you are working on question 2.1. If however, you are working on question 2.2 or 2.3, then replace 2.1 in the instructions with 2.2 or 2.3 respectively. 1 Use the BlueJ project at: h:\ci101.exam_place-number\2.1 to modify/construct and debug your program. Remember to include your student number in a comment at the top of this Java program file 2 Once you are convinced your program works in BlueJ From the start (icon bottom left corner) select the search dialogue box replacing 'search programs and files' with cygwin. Select 'cygwin bash shell' and then at the newly created windows command prompt type: cd h:/ci101.exam_place-number sh check.sh 2.1 Note The use of/ instead of \ in the path This process runs a check on the program using several sets of data and is similar to the checks that take place on the Charon system. That's it, now leave all the files alone in the directory 2.1. The files will be collected after the exam finishes and the test(s) rerun. M A Smith University of Brighton December 6, 2016 Page 24