Final Exam. CSC 121 Fall 2015 MW. Lecturer: Howard Rosenthal. Dec. 16, 2015

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1 Your Name: Final Exam. CSC 121 Fall 2015 MW Lecturer: Howard Rosenthal Dec. 16, 2015 The following questions (or parts of questions) in numbers 1-17 are all worth 2 points each. The programs have indicated point values. There are 2 programs to write. There are 112 points on this test which means you can earn up to 12 extra points towards your test average. Remember that only the Command Box and Notepad++ with no other programs available may be open until you are ready to the programs. You are allowed to bring 2 double sided or 4 single sided sheets into the test with you. On the last two sheets you will find the ASCII character to decimal conversion, and some common String methods. You can detach these sheets for easier use. 1. Answer the following as true or false. _F a. Reserved words can be overloaded and used as reference variables. _T b. short and char variables use the same number of bits. _T c. ( JOHN.compareTo( John ) <0) evaluates as true. _T d. (true&&(true&&false)) always evaluates as false. _F e. Classes are instantiations of objects. _F f. Array indices can be expressed as char values that will automatically cast up to type int. _F g. Every row of a two dimensional array must be of the same length. _F h. A method s signature includes its name and its return value. _F i. ( AB == ( A + B )) evaluates as true. _F j. The output of the java compiler is a.class file in Unicode. _T k. If the pattern String is applied during output it guarantees that the printed number will always display three decimal places. 1

2 2. Write -61 in two s complement using 8 bits What is the decimal value of ? The bundling of data and methods into classes is known as _encapsulation. 5. Given the following array: table ={{1,4,7,9,11}, {1,2}, {1,2,0}, {4,9,8,6,3,16}} What is the value of table.length? 4 2

3 6. List two different ways that methods can be overloaded. a. Different number of formal parameters b. Different types of parameters in corresponding positions 7. Write the output from this code segment: String growth = ABC ; int sum = 0; for (int i=0; i <growth.length(); i++) { sum = sum + growth.charat(i); } System.out.println(sum); To use the File class you must import from which package?.java.io 9. Given: double x = ; and the format pattern is the printed output String will be

4 10. What is the output of the following code fragment? int j=10, k=0; while(j>3) { System.out.print(k + ); k=k + (j%3); j=j -1; } For the String text = Hellotoday ; text.substring(4) has the value otoday. 12. How many bytes does the following statement reserve for the array called sarray: double[][] sarray = new double[3][4]; Write a statement that instantiates a two-dimensional String array called quotes with 6 rows and 4 columns. String [][] quotes = new String[6][4]; 14. System.out.println (( A + 2) + +(4+8)); prints out as

5 15. Draw the following array on a row by row basis char [] [] puzzle = new char [3][5]; char letter = a ; for (int i=0; i <3; i++) { for (int j=0; j<5; j++) { puzzle [i][j] = letter; letter = (char)(letter+1); } } a b c d e f g h i j k l m n o 16. Assume static Random coin = new Random(); Write a statement that simulates a coin flip with a 0 representing a heads and a 1 representing a tails. Place the result in an int called flipper. int flipper = coin.nextint(2); 17. How many objects are present after the following code fragment has executed? String str1 = Dog ; String str2 = new String ( Dog ); String str3 = new String( Dog ); String str4 = Dog ; 3 Programs: 5

6 It is important to follow the instructions in each problem. two.java files to Do not mail these files until you are done with the entire exam. No second mailing will be allowed. 1. CountChars (28 points) Write the following program. In the main method: Prompt the user for the dimensions of a two-dimensional array. Create a two-dimensional char array called chararray. Call a method name fillarray, sending it a reference to the chararray. Call a method called countchars which returns a reference to an int array called charcount of length 26. Print out the array a row at a time with a space between each character. Print out the following header followed by the results of charcount one line at a time. It will look like this Letter Count A no of A s B no of B s.... Z no of Z s. In fillarray method: Fill the two-dimensional char array (reference is sent as a formal parameter) with capital letters that are randomly generated. Remember that capital letters can be generated randomly by generating randomly integers between 65 and 90. In countchars method: Accept the reference to the randomly generated char array, and count the number of characters of each type. Return a reference to an int array called charcount of length 26 where charcount[0] has the number of A s in the two-dimensional array, charcount[1] has the number of B s in the two-dimensional array, etc. 6

7 2. CleanString (28 Points) Write the following program. You will be reading from a file that is formatted with a new string on each line. In the main method: Prompt for the name of the input and output files. Set up the appropriate objects to read and write from those files Read one line at a time from the file into a String array called origstr, assuming that there are a maximum of 100 lines in the input file. (Note: origstr has references to up to 100 Strings.) Once all the lines in the file are read into origstr call a method called clean. The formal parameters to clean are a reference to origstr, and the number of Strings to be cleaned, that is, the number of Strings read in from the input file. The return value will be a reference to a different String array, as described below. Call that array cleanedupstr. For each member of cleanedupstr referenced in the return from the clean method, write that cleaned String followed by a space followed by the length of the cleaned up String on a single line of the output file. In the clean method: Create formal parameters for the reference to the array called inputstr, and the number of Strings read in called no_inputs. Create a new String array called cleanstr with a length equal to no_inputs.. For each String referenced in inputstr, capitalize the String and remove all non-alpha characters, and place a reference to the cleaned String in the cleanstr array. The Strings should correspond by index, that is the value of cleanstr[i] should be the cleaned up String of inputstr[i]. Return the reference to the cleanstr array. See Sample on next page Sample 7

8 If the input file looks like this: String 1 abcdef gh!! XXcd45670-!A I Am A JAVA NERD Let's program two - Ernie Banks 4 times 4 = 16 Then the output file would look like this: STRINGABCDEFGH 14 XXCDA 5 IAMAJAVANERD 12 LETSPROGRAMTWOERNIEBANKS 24 TIMES 5 8

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12 Common String Methods str.charat(k) str.substring(k) s.substring(k, n) str.indexof(s) str.indexof(s, k) str.startswith(s) str.startswith(s, k) str.equals(s) returns a char at position k in str. returns a substring from index k to the end of str returns a substring from index k to index n-1 of str returns an index of the first occurrence of String s in str returns an index of String s starting an index k in str returns true if str starts with s returns true if str starts with s at index k returns true if the two strings have equal values str.equalsignorecase(s) same as above ignoring case str.compareto(s) compares two strings s.comparetoignorecase(t) same as above ignoring case s.touppercase() Returns String s with any lower case alpha changed to upper case 12