IT 313 Advanced Application Development Midterm Exam

Transcription

1 Page 1 of 9 February 12, 2019 IT 313 Advanced Application Development Midterm Exam Name Part A. Multiple Choice Questions. Circle the letter of the correct answer for each question. 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 or work will not be considered. Answer only 13 out of 14 questions. If you answer all 14 questions, only the best 13 responses will be graded. 5 points for each question. 1. Which of these statements converts the String object s into the char value c? a. c = (char) s; b. c = Character.parseChar(s) c. Character.valueOf(s) d. c = s.charat(0) 2. Which of the following primitive datatypes takes up 2 bytes in memory? a. boolean b. char b. double d. int 3. If s and t are defined as reference variables for String objects, when does the expression s.equals(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. 4. The process of changing the source code of a project without affecting its functionality is called a. compiling b. preprocessing c. refactoring d. transposing 5. What are overloaded methods? a. Methods with the same name in the same class, but different return value datatypes. b. Methods with the same name in the same class, but different signatures. c. Methods with the same name and same return value datatype, but in different classes. d. Methods with the same name and same signature, but in different classes. 6. Which statement instantiates a new java.util.calendar object? Assume the import statement import java.util.calendar; a. cal = Calendar.instanceOf( ); b. cal = Calendar.getInstance( ); c. cal = new Calendar.getInstance( ); d. cal = new Calendar( );

2 Page 2 of 9 7. Which of these statements creates a Color object c that represents maroon? a. Color c = new Color(0x800000); b. Color c = new Color(0x008080); c. Color c = new Color(0xff0000); d. Color c = new Color(0xffffff); 8. Which of these statements creates a Scanner object that reads from the input file numbers.txt? a. Scanner s = new Scanner.InstanceOf("numbers.txt"); b. Scanner s = new Scanner(new File("numbers.txt")); c. Scanner s = new Scanner(new File("numbers.txt")) throws FileNotFound Exception; d. Scanner s = new Scanner("numbers.txt"); 9. What does JAR mean for a JAR file? b. Java Accumulating Register b. Juxtaposed Actual Relationship c. Java Application Resource d. Java Archive file 10. What is the correctly defined getter method for the _animaltype instance variable? a. public String getanimaltype(string theanimaltype) { _animaltype = theanimaltype; b. public void getanimaltype(string theanimaltype) { return _animaltype; c. public void getanimaltype(string theanimaltype) { theanimaltype = _animaltype; d. public void getanimaltype(string theanimaltype) { System.out.println(_animalType); 11. Define a collection like this: ArrayList<Person> col = new ArrayList<Person>( ); Which statement correctly prints the age of the item with index 57? a. System.out.println(col.[57]._age); b. System.out.println(col.get[57]._age); c. System.out.println(col[57].getAge( )); d. System.out.println(col.get(57).getAge( ));

3 12. This problem is more difficult that most of the other problems. Here are definitions of the classes MyClass and the unit test file Test2: // Source code file MyClass.java import java.util.arraylist; public class MyClass { public static int mymethod(arraylist<integer> values) { int total = 0; for(int n : values) { total += n * n; return total; // Source code file MyClass.java import static org.junit.jupiter.api.assertions.*; import java.util.arraylist; import org.junit.jupiter.api.beforeeach; import org.junit.jupiter.api.test; class Test2 { ArrayList<Integer> _col; Page 3 of void setup() { _col = new ArrayList<Integer>( ); int[ ] arr = {2, 3, 5, 7; for(int v : arr) { _col.add(v - 2); Which of the unit test methods on the top of Page 4 succeeds? a. Method a b. Method b c. Method c d. Method d

4 Page 4 of 9 # Method void test() { assertequals(myclass.mymethod(_col) + 1, 10); # Method void test() { assertequals(myclass.mymethod(_col) + 2, 18); # Method void test() { assertequals(myclass.mymethod(_col) + 3, 38); # Method void test() { assertequals(myclass.mymethod(_col) + 4, 91); 13. How is inheritance indicated in the Java class header for the derived class Boat? a. public class Boat extends Vehicle { b. public class Boat inherits Vehicle { c. public class Boat super Vehicle { d. public class Boat : Vehicle { 14. What happens if the definition of the tostring method is removed from the Pet class and these statements are executed: Pet = new Pet("Mimi", "Cat", "Susan", 'F'); System.out.println(pet); a. An empty string ("")is printed. b. The error message Unresolved compilation problem, is produced. c. The program throws the exception ObjectNotFoundException. d. The tostring method from the base class, which in this case is Object, executes instead of the tostring method that was removed.

5 Page 5 of 9 Part B: Correct the Errors. There are about 7 errors in each of the two files GroceryItem.java (Page 5), and LoadGroceryItems.java (Page 6), for about 14 total errors. Correct the errors directly on these sheets; do not recopy. Inserting, correcting, or removing a pair of ' ', " ", ( ), [ ], or { only counts as one error. 15 points. // Source code file: GroceryItem.java package it313.midterm { private class GroceryItem { private int _code; private String _description private double _price; private boolean _onsale; public GroceryItem(int thecode, String thedesc, double theprice) { _code = thecode; _description = thedesc; price = theprice; _onsale = false; public int isonsale( ) { return _onsale; public void setonsale(boolean boolval) { if (!_onsale && boolval) { _price *= 0.5; else if (_onsale &&!boolval) { _price *= 2.0; _onsale = boolval; Override public int tostring( ) { return String.format("%d %s %.2f %s", _code, _description, _price, _onsale);

6 Page 6 of 9 // Source code file LoadGroceryItems.java import java.io.file; import java.io.filenotfoundexception; import java.util; import it313.midterm; public class LoadGroceryItems { public static void main(string args) { GroceryItem item = new GroceryItem(11111, "Oranges", 3.45); System.out.println(item); GroceryItem[ ] items = new GroceryItem[8]; File f = new File("groceries.txt"); Scanner input = null; try { Scanner input = new Scanner(f); catch (FileNotFoundException e) { System.out.println("Input file groceries.txt not found"); System.exit(1); int arrayindex = 0; while(input.hasnextline( )) { String line = input.nextline( ); String[ ] fields = line.split(","); int code = Integer.parseInt(fields[0]); String desc = fields[1]; double price = Double.parseDouble(fields[3]); items(arrayindex) = new GroceryItem(code, desc, price); arrayindex--; for(groceryitem i : items) { if i!= null { i.setonsale(true); System.out.println(i); input.close( );

7 Page 7 of 9 Part C: Write Instance Methods. 5 points each. 1. Write the getter for the _price instance variable in the GroceryItem class defined on Page Write the setter for the _price instance variable in the GroceryItem class defined on Page 5.

8 Page 8 of 9 Part D: Predict the Output. Predict the output of the main method on this page. It uses the Clock class defined on Page 9, which keeps track of the date as well as the time. Show your work. 10 points. // Source code file: TestClock.java public class TestClock { public static void main(string[ ] args) { Clock c1 = new Clock(2019, 2, 13, 23, 59, 50); Clock c2 = new Clock(2019, 12, 31, 23, 59, 55); for(int i = 1; i <= 20; i++) { c1.tick( ); c2.tick( ); for(int i = 1; i <= 60; i++) { c2.tick( ); System.out.println(c1); System.out.println(c2); Show your output for Problem D. Explain how you obtain your answer.

9 Page 9 of 9 // Source code file: Clock.java public class Clock { private int _year, _mon, _day, _hour, _min, _sec; // _day and _month are one-based. public Clock(int y, int mo, int d, int h, int m, int s) { _year = y; _mon = mo; _day = d; _hour = h; _min = m; _sec = s; public void tick( ) { int[ ] days_in_month = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31; _sec++; if (_sec >= 60) { _sec = 0; _min++; if (_min >= 60) { _min = 0; _hour++; if (_hour >= 24) { _hour = 0; _day++; if (_day > days_in_month[_mon]) { _day = 1; _mon++; if (_mon > 12) { _mon = 1; public String tostring( ) { return String.format("%d/%d/%d %02d:%02d:%02d", _mon, _day, _year, _hour, _min, _sec);