Final Exam. CSC 121 Fall Lecturer: Howard Rosenthal. Dec. 13, 2017

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1 Your Name: Final Exam. CSC 121 Fall 2017 Lecturer: Howard Rosenthal Dec. 13, 2017 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 114 points on this test which means you can earn up to 14 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 1 double-sided or 2 single-sided sheets into the test with you. On the last sheets you will find the ASCII character to decimal conversion, and some common String methods. You will also find model code that you can use for input and output from files. You can detach these sheets for easier use. 1. Answer the following as true or false. a. Objects created from the String class are immutable. b. double and long variables use the same number of bytes. c. ( JOHN.equals( John ) ) evaluates as true. d. (false&&(true false)) always evaluates as false. e. An object is instantiated from a class. f. Array indices can be expressed as boolean values since arrays sometimes store boolean values. g. When an array of String objects is created every cell is initialized to the integer 0. h. Every method must return a value. i. ((65 + B ) == ( A + B )) evaluates as true. j. An if-else block can be nested inside a for loop block. k. A reference variable for an object is always initialized to null when it is created. 1

2 2. What is the decimal value of ? 3. Write -79 in two s complement using 8 bits. 4. The object-oriented language feature that packages attributes and behaviors into a single unit is called 5. Given the following array: int [][] table =1,4,7,9,11, 1,2, 1,2,0, 4,9,8,6,3,16; What is the value of table[3].length? 6. In which package is the PrintWriter class found? 7. If String text = MyNameIsAnakin then the value of text.substring(2,7) is. 8. How many bytes does the following statement reserve for the cells in the array called strarray: String[] strarray = new String[8]; 2

3 9. Provide examples of two different ways that methods can be overloaded a. b. 10. The java compiler produces a file with the extension that is used as input to the JVM. 11. Write a method header for a method called cointoss with two formal parameters int number and String str that returns a boolean value. 12. The value of ( ABCD.length() + e.length()) is. 3

4 13. What is the output of the following code fragment? for ( int i = 6; i < 10; i++ ) for (int j=3; j<=5; j++) System.out.printf( %d, (i%j) ); 14. What is the printout from the following code segment: String growth = ABC ; char letter = d ; for (int i=0; i <4; i++) growth = growth + letter; letter = (char)(letter+2); System.out.printf( %s\n, growth); 4

5 15. Assume the Random class has been imported and that Random randy = new Random(); Write a statement that randomly selects an integer from 2,3,4,5,6,7,8 and assigns it to the variable int number. You must use the randy object to do this. 16. How many String objects are created by executing the following code fragment? String str1 = Dog ; String str2 = new String ( Dog ); String str3 = Dog ; String str4 = str3; 5

6 Programs: 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. Note: Use the method names I have suggested. The array names and other variables don t need to be the same, although it may make it easier for you as you write your programs. They just made it easier to explain subsequent steps. 1. UpperAlphaCount (24 points) Write a program with two methods. main: (12) Prompts for the number of String(s) to read in. Read in a String using nextline() before entering the loop in order to move to the next line. This simply moves you to the next line so you can start reading in full lines. For each String to be read in: Prompts the user to enter a String that is read into the row corresponding to that iteration of the loop. Hint: use nextline() Passes the String reference to the method countuppercase, and accepts an int returned by countuppercase. Prints the : The String str has num upper case alpha characters. countuppercase: (12) Accepts a reference to a String. Counts the number of upper case alpha characters in the String. (This sentence requires a loop to implement). (Hint: Remember the range for apha upper case letters in ASCII). Return the count of upper case alpha characters. 6

7 2. SearchForName (36 Points) Write a program that does the following. Use the model program segments for creating Scanner and PrintWriter objects. Remember that some of the inputs and outputs come directly from the keyboard and to the terminal. main: (13) Calls createarray and accepts as a return value a reference to a one-dimensional String array called namelist with length 100. Prompts for the name of a file with a list of up to 100 names, with only one name on each row. You will need to create a file with one name per row in the same directory that your program is in. You may assume that there are no more than 100 names in the list, and that each name has no more than 9 characters. Sets up a Scanner to read from the input file. If the file doesn t exist there should be a soft exit. Prompts for the name of an output file. Sets up a PrintWriter so that it can write to that output file. Reads in a list of names from the input file into the String array namelist. (Hint: need to keep track of the cell in the array you are writing into within this loop, starting from 0, and the total number of cells that you have read into) Requests a name to search from the user via the terminal. (Use next() instead of nextline() to avoid any problem here) Calls the method called findname with three parameters: - a reference to the String array strarray - a reference to the String with name being searched for - an int parameter with the number of names that have been read into the String array Accepts back from findname a boolean value. Prints out a line to the screen that says: It is true/false that the name is found in the list of names in filename. Writes the capitalized version of each of the names in the array into the output file, along with its length, with each pair on its own line. A line in the output file might look like this if the input lines were Felix Leonard Then the output file would look like this FELIX 5 LEONARD 7 createarray: (10) Creates a one-dimensional String array of length 100, and return a reference to the array. findname: (13) Accepts three parameters including: - a reference to a one-dimensional String array strarray - a reference to the String with name being searched for - an int parameter with the number of names that have been read into the String array Searches to determine if the name is found in the list of names. Returns true if the name is found on the list, false otherwise. Ignore capitalization when doing your compares, i.e. Elmer and ELmER should be considered a match. 7

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10 Some or all of these pieces of code may prove helpful. //Required import files when using input and out files import java.util.scanner; import java.io.file; import java.io.printwriter; import java.io.ioexception; public static void main(string[] args) throws IOException //Input File Code Segment System.out.printf("Please enter name of file to encrypt: "); String inputfilename=keyboard.next(); File inputfile = new File(inputFileName); //housekeeping to create target file input scanner if(!inputfile.exists()) System.out.printf("Input File %s was not found.\n", inputfilename); System.exit(0); Scanner inputreader = new Scanner(inputFile); // Output File Code Segment System.out.printf("Please enter name of file to write encryption to: "); String outputfilename=keyboard.next(); File outputfile = new File (outputfilename); //housekeeping to create target file printer PrintWriter outputwriter = new PrintWriter(outputFile); //Possible Structure for reading in data while (inputreader.hasnext()) //You would have to put in code here //For Closing Files inputreader.close(); outputwriter.close(); 10

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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) str.equalsignorecase(s) str.compareto(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; an unsuccessful search returns -1. returns an index of String s starting an index k in str; an unsuccessful search returns -1. 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 same as above ignoring case compares two strings s.comparetoignorecase(t) same as above ignoring case s.touppercase() Returns the String with all alpha characters in upper case 12