CSIS 10A Practice Final Exam Name:

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1 CSIS 10A Practice Final Exam Name: Multiple Choice: Each question is worth 2 points. Circle the letter of the best answer for the following questions. 1. For the following declarations: int area; String name; Which of the following is true? a. area is a primitive variable, and name is an object reference variable. b. area is an object reference variable, and name is a primitive variable. c. both are primitive variables d. both are object reference variables 2. In the following section of code: int area; String name; How many objects have been created? a. None---there is one object reference variable, but no objects yet. b. One---there is one object reference variable so there must be one object. c. Two---one for each variable. d. Two---one for each type. 3. A startup class is the class that contains the method where execution of the program begins. a. void b. main c. String d. first 4. A(n) is a set of instructions for solving a class of problems by a mechanical process. a. parameter c. method b. list d. algorithm 5. Java allows you to create new kinds of objects by defining a new file that shows how the objects are defined and used. a. object c. class b. data d. main 6. Which of the following declares an array of int named img? a. int img; c. new int img[]; b. int[] img; d. int img = int[]; 7. What is the meaning of null? a. It is another name for zero. b. It is the String object that contains no characters. c. A reference variable that contains null is not referring to an object. d. It is a special value used to indicate an error condition.

2 8. What is the output of the following code fragment: int[] ar = {2, 4, 6, 8 ; ar[0] = 23; ar[3] = ar[1]; System.out.println( ar[0] + ", " + ar[3] ); a. 23, 2 c. 0, 3 b. 2, 8 d. 23, 4 9. For which of the following applications is an array NOT suitable: a. Holding the scores on twelve midterms exams of a class. b. Holding the name, social security number, age, and income of one individual. c. Holding the temperature readings taken every hour throughout a day. d. Holding the total sales a store made in each of twelve months. 10. What does the following statement do? String[] widget; a. It declares an array of references to widget objects named String. b. It creates a String object named widget. c. It creates an array of length zero named widget. d. It declares a variable widget which may in the future hold a reference to an array of references to String objects but is initialized to null. 11. A(n) method is a method that is invoked on an object, and that operates on that object. a. object b. class c. void d. constructor 12. The term refers to the practice of hiding the details of an object from the other parts of a program a. obfuscation c. compilation b. data mining d. encapsulation Short Answer: Each question is worth 2 points. Fill in the blanks with the best answer. 13. A is an item of data supplied to a method when the method is invoked. 14. All objects have a method that returns a string representation of the object. 15. An object that has no references to it is called 16. If several reference variables refer to the same object, each variable is said to be an of the object. 17. To check if two reference variables both refer to the same object, use the operator. 18. To check if two different objects contain equivalent data, use the method.

3 Code Reading Problems: Determine the output of the following code examples. Each question is worth 10 points. 19. public class Dog{ String name; int age; public Dog(){ name = "----"; age = 0; public Dog(String name, int age){ this.name = name; this.age = age; public void speak(){ if (age < 1) System.out.println("yap!"); else System.out.println("ruff!"); OUTPUT Dog fido = new Dog(); Dog rex = new Dog("Rex", 2); fido.speak(); rex.speak(); fido.age = rex.age; fido.speak(); 20. public static void dub(int[] jub) { for (int i = 0; i < jub.length; i++) { jub[i] *= 2; public static int mus(int[] zoo) { int fus = 0; for (int i = 0; i < zoo.length; i++) { fus = fus + zoo[i]; return fus; OUTPUT public static void main(string[] args) { int [] dat = {2,4,5,1,8; dub(dat); for (int i = 0; i < dat.length; i++) System.out.print( dat[i] + " "); System.out.println("\n mus = " + mus(dat));

4 21. OUTPUT public class Figure{ Point [] fig = new Point[5]; for (int k=0; k<fig.length; k++) fig[k] = new Point(k*100, k*100); fig[0] = fig[4]; System.out.println(fig[0].x + ", " + fig[0].y); System.out.println(fig[4].x + ", " + fig[4].y); Coding Writing Problems: Fill in the blanks where indicated with code that completes the specified task. 22. (15 points) A Box object represents a cardboard box with length, width and height. Complete the definition of the Box class so the program produces the desired output shown. public class Box { int length, width, height; // a) write the no-arg constructor here, all sides set to 0 // b) write the parameterized constructor here, take length, width, height // c) setheight: change the height of a box object to a new height // d) vol: return the volume of a box object (the product of all three sides) DESIRED OUTPUT Box big = new Box(); // uses method a) Box carton = new Box(3,5,8); // uses method b) carton.setheight(4); // uses method c) System.out.println("big vol = " + big.vol()); // d) big vol = 0 System.out.println("carton vol= " + carton.vol()); carton vol = 60

5 23. (15 points) Arrays: For the following program, write the statements where indicated to perform the the specified tasks. DESIRED OUTPUT int [] arra = {5,7,3,9,2; int [] arrb = {8,5,2,5,9; // a) declare and create arrc, an array of int the same size as arra // b) write a loop to traverse the arrays. At each index, copy the // larger of the corresponding values (arra or arrb) into arrc print(arrc); 8, 7, 3, 9, 9 // c) write a method below to compute and return the total // sum of the first N values in an array System.out.println("SumA = " + sum(arra, 3)); SumA = 15 System.out.println("SumB = " + sum(arrb, 2)); SumB = 13 System.out.println("SumC = " + sum(arrc, 1)); SumC = 8 public static void print(int [] arr){ for (int k=0; k<arr.length; k++) System.out.println(arr[k] + ", "); System.out.print("\n"); // write your method for c) here

6 24. (5 Points) Arrays of Objects For this program, add statements where indicated to perform the desired tasks using the given methods. public class Account{ private String name; private double balance; public Account(String name, double balance){ this.name = name; this.balance = balance; public double getbalance(){ return balance; public void deposit(double amount){ balance = balance + amount; // d) write the tostring method for Account (see part e below) Account[] bank = new Account[4]; bank[0] = new Account("Sal", ); bank[1] = new Account("Abe",202.12); bank[2] = new Account("Tim", ); bank[3] = new Account("Deb",104.12); // a) write a statement that deposits $50 in Abe s account DESIRED OUTPUT // b) write a statement that prints Abe s balance // c) write a loop that deposits $50 only in those // accounts with more than a $500 balance // e) write a loop that prints out all four bank accounts // using your tostring method from above Sal $ Abe $ Tim $ Deb $104.12