IT 313 Advanced Application Development

Transcription

1 Page 1 of 9 IT 313 Advanced Application Development Midterm Exam February, 12, 2018 Name Part A. Multiple Choice Questions. Answer all questions. Optional: supply a reason or show work for partial credit in case you select the wrong answer. If you select the correct answer, your reason of work will not be considered. 5 points for each question. 1. Which of the following datatypes takes up 8 bytes in memory? a. boolean b. double c. int d. octal 2. If s and t are defined as reference variables for String objects, when does the expression s == t return true? When a. s and t contain the same memory address. b. the String objects referenced by s and t both have the same length. c. the String objects referenced by s and t contain the same characters. d. When the string objects referenced by s and t contain the same characters when converted to upper case. 3. The process of changing the source code of a project without affecting its functionality is called a. compiling b. preprocessing c. refactoring d. transposing 4. Two methods that are defined within the same class with the same names, but with different signatures are called methods. a. overridden b. overloaded c. protected d. static 5. Which statement converts the int value n into the String object t? a. t = n.tostring( ); b. t = n + ""; c. t = String.parseString(n); d. t = (String) n; 6. Which Java keyword or symbol is used to show that a class is a derived class of a base class? a. < b. base c. extends d. super

2 Page 2 of 9 7. Which of these is the best definition for the tostring method for the Student class with instance variables _name, _year, and _gpa. public String tostring { return _name + _year + _gpa;; public String tostring( ) { return _name, _year, _gpa; public String tostring( ) { return String.format("%s %d %.3f", _name, _year, _gpa); public tostring( ) { System.out.println(_name + _year + _gpa); 8. The collection col is defined as ArrayList<String> col = new ArrayList<String>( ); Which statement sets the ArrayList item with index 3 to "Chicago"? a. ArrayList.set(col, 3, "Chicago") b. col.set(3, "Chicago"); c. col.set[3] = "Chicago"; d. col.set(3) = "Chicago"; 9. The findmaxindex method finds the index of the largest item in the int array. In case of a tie for the largest item, the first index of the tied items is returned. The source code for the findmaxindex method is shown on the next page:

3 Page 3 of 9 public class TestMethod { public static int findmaxindex(int[ ] array) { int maxindex = 0, val = array[0]; for(int i = 1; i < array.length; i++) { if (array[i] > val) { val = array[i]; maxindex = i; return maxindex; Which of these is a correct Junit test method from a Junit Test project that tests the findmaxindex method? void test( ) { int[ ] a = {3, 6, 5, 8, 6, 7; assertequals(3, Main.findMaxIndex(a)); void test( ) { int[ ] a = {3, 6, 5, 8, 6, 7; assertequals(8, Main.findMaxIndex(a)); void test( ) { int[ ] a = {3, 6, 5, 8, 6, 7; assertequals(3, Main.findMaxIndex(a[ ])); void test( ) { int[ ] a = {3, 6, 5, 8, 6, 7; assertequals(8, Main.findMaxIndex(a[ ]));

4 Page 4 of How is the package that contains the Java class A specified? Suppose that the package name of the class A is it313.proj4. a. import it313.proj4; public class A { // body of class A b. import it313.proj4{ public class A { // body of class A c. package it313.proj4; public class A { // body of class A d. package it313.proj4 { public class A { // body of class A 11. Which of these statements defines a HashMap collection using keys of datatype String and storing values of datatype Transaction? a. HashMap col = new HashMap(String, Transaction); b. HashMap<String> col = new HashMap<String>(Transaction); c. HashMap<Transaction> col = new HashMap<Transaction>(String); d. HashMap<String, Transaction> col = new HashMap<String, Transaction>( ); 12. Which HashMap method is used to insert a new item into the collection? a. add b. insert c. put d. set

5 Page 5 of 9 Part B: Reorder Source Code Lines. The source code file GetExchangeRate.java is supposed to input one of the target currencies CAD, CHY, EUR, GBP, or MXN and the source amount. It then reads the exchange rate from the corresponding text file in the project folder and computes the target amount from the exchange rate and source amount. 10 points. Here are the contents of the text files: Filename Exchange Rate cad.txt chy.txt eur.txt gbp.txt mxn.txt Several lines of the source code file GetExchangeRate.java shown below are out of place. Draw arrows to show where the out of place lines should be placed. For example, the arrow shows where the out of place line in the HelloWorld class should be placed: public class HelloWorld { public static void main(string[ ] args) { System.out.println("Hello, World."); // --- Source code file: GetExchangeRate.java import java.util.scanner; import java.io.file; public class GetExchangeRate { public static void main(string[ ] args) throws FileNotFoundException { import java.io.filenotfoundexception; double exchangerate = Double.parseDouble(fromFile.nextLine( )); Scanner fromkeyboard = new Scanner(System.in); Scanner fromfile = new Scanner(new File(fileName)); System.out.print("Enter target currency " + "(CAD, CHY, EUR, GBP, or MXN): "); String targetcurrency = fromkeyboard.nextline( ); System.out.print("Enter source amount: "); double sourceamount = Double.parseDouble(fromKeyboard.nextLine( )); String filename = targetcurrency.tolowercase( ) + ".txt"; double targetamount = exchangerate * sourceamount; System.out.println("Target Amount: " + targetamount); fromfile.close( ); fromkeyboard.close( );

6 Page 6 of 9 Part C: Correct the Errors. There are about 5 errors in each of the three files OutcomeSet.java (this page), DiceSet.java (Page 7), and OutcomeSetTest.java (Page 7). Correct these errors. Inserting, correcting, or removing a pair of ' ', " ", ( ), [ ], or { only counts as one error. 15 points. // Source code file: OutcomeSet.java imports java.util.arraylist; public class OutcomeSet { // protected means that the instance variable is visible // to this current class and also its derived class DiceSet. protected int _capacity; protected ArrayList<Integer> _outcomes; // Constructor for this class. public OutcomeSet(int thecapacity) { _capacity = thecapacity; outcomes = new ArrayList<Integer>(theCapacity); public int getcapacity( ) { return _capacity; // Add an outcome to the ArrayList collection. public void addoutcome(int theoutcome) { if (_outcomes.size( ) < _capacity) { _outcomes.add(theoutcome); // Clear all outcomes from the ArrayList collection. public void clear( ) { _outcomes.clear( ); // OutcomeSet public String tostring( ) { String output = ""; for(int value in _outcomes) { output = value + " "; return output;

7 Page 7 of 9 // Source code file: DiceSet.java import java.util.random; public class DiceSet extends OutcomeSet { // _rangen is a reference to a random number generator. // _rangen.nextint(n) returns a random integer between // 0 and n 1, inclusive. Random _rangen; // numdicesides is the number of faces on each die. /* For example, a standard die has six faces. Int _numdicefaces; public DiceSet(int thecapacity, int thenumdicefaces) { super(thecapacity); _rangen = new Random( ); _numdicefaces = the_num_dice_faces; public rolldice( ) { _outcomes.clear( ); for(int i = 0; i < this.getcapacity( ); i++) { _outcomes.add(_rangen.nextint(_numdicefaces) + 1) // Source code file: DiceSetTest.java public class DiceSetTest { public static int Main(String[] args) { OutcomeSet os = new OutcomeSet("5"); for(int i = 1, i <= os.getcapacity( ), i++) { os.addoutcome(i); System.out.println(os); DiceSet ds = new DiceSet(5, 6); ds.rolldie( ); System.out.println(ds);

8 Page 8 of 9 Part D: Test Methods from Java Class Library. Documentation from the Java Class Library for the Currency class is shown on Page 9. Write traditional tests or JUnit tests for 4 of the Currency instance methods. Note that there is no constructor for the Currency class. For 3 points extra credit (13 total points), write both traditional tests and unit tests. Write your traditional and Junit tests on this page (Page 8). Abridged documentation for the Currency class is shown on Page points. === Traditional tests ======================== public static void main(string[ ] args) { === Junit tests ============================== import static org.junit.assert.*; import org.junit.before; import org.junit.test; public class MainTest public void test( ) {

9 Page 9 of 9 Java Class Library Documentation for the Currency Class Package: java.util Constructor No constructor is available for the Currency Class. Some Instance Methods and Descriptions String getcurrencycode() Returns the ISO 4217 currency code of this currency, for example: CAD, EUR, GBP, MXN, USD. int getdefaultfractiondigits( ) Returns the default number of fraction digits used with this currency, which is 2 for each of the currencies CAD, EUR, GBP, MXN, USD. String getdisplayname( ) Returns the name that is suitable for displaying this currency, for example: Canadian Dollar, Euro, British Pound Sterling, Mexican Peso, US Dollar. static Currency getinstance(string currencycode) Returns a Currency object for the given currency code, for example: CAD, EUR, GBP, MXN, USD. int getnumericcode( ) Returns the ISO 4217 numeric code of this currency. String tostring( ) Returns the ISO 4217 currency code of this currency, for example: CAD, EUR, GBP, MXN, USD.