CSC 111, Test 1 (Fall 2009)

Transcription

1 CSC 111, Test 1 (Fall 2009) Name There are 8 questions, many with sub-questions, as part of this test. Make sure you read and answer each question carefully and fully. Partial credit, while possible, will not be given for work that is not on-task for the question. This exam is to be done individually according to the honor code at Wake Forest University. Problem 1. Below you will find a Java program, with each instruction of interest numbered. Read the program and answer the questions that follow at the top of the next page. import javax.swing.*; public class SampleProgram static int methoda(int value) 1 int answer; 2 boolean resultfromc = methodb(value); 3 if (resultfromc == true) 4 return value * value; 5 else 6 answer = value / 10; 7 return answer; static boolean methodb(int value) 8 return (value * value < 100); public static void main(string[] args) 9 int x; 10 int y; 11 String response; 12 String inputvalue = JOptionPane.showInputDialog(null, "Enter an integer: ", "Frame Title", JOptionPane.QUESTION_MESSAGE); 13 x = Integer.parseInt(inputValue); 14 y = methoda(x); 15 response = "The output value is " + Integer.toString(y); 16 JOptionPane.showMessageDialog(null, response, "SampleProgram", JOptionPane.INFORMATION_MESSAGE);

2 A. Indicate, by listing line numbers, the order of instructions as they are executed. Assume the value the user types in when the dialog box appears asking for an integer on line twelve is the value 15. B. If there are certain instructions that may not execute during a running of this program, indicate the line numbers of those instructions and the cause (state of the program) for them not being executed. Problem 2. For each situation below, specify a variable type, name, and value which would be appropriate for the situation described. Make sure you use correct declaration and initialization syntax. A. The name of the street on which you grew up B. The cost of your textbooks for the Fall semester C. The number of students enrolled in this class D. The flight time (in hours) for a cross country plane trip

3 Problem 3. Here s a Java program that will compile and execute without errors. Indicate the value of each underlined variable after the statement that the variable is underlined in is executed. public class TestProblem public static void main(string[] args) double v1 = 4; double v2 = 6; double v3 = 12; double t = v2 10; // -4 double x = 9 - v3; // -3 boolean n1 = (v1 10) >= 0; // false boolean n2 =!(t < 0); // false boolean n3 = (x == 0) (x < 0); true boolean at = (n1 == true) && (n2 == true) && (n3); // false double mp = 0; if (at == true) // it doesn t equal to true mp = 1000; // skipped else // n3 is true if ((n1 == true) (n2 == true) (n3 == true)) mp = 10; // executed System.out.println(mp); A. Value of at: B. Value of mp:

4 Problem 4. List the types and names of and describe why you chose at least four variables that might be useful in defining a class to model a SpeedingTicket, given that you need to represent information about a speeding ticket similar to the following: Ticket #92476 was issued to Mr. Thomas Smith by Officer Cynthia Jones. This ticket, for the offense of driving 10+ mph over the speed limit, was issued on May 25, 2008 and requires payment of a $ fine. Problem 5. Answer the following questions dealing with concurrency. A. From your life's experience, give a real-world simple example of the use of concurrency. B. Indicate whether or not your example of concurrency required synchronization between the tasks (threads) being executed. If so, explain how synchronization occurred; otherwise, explain why it wasn t required. C. Assume that your task did require synchronization. Suggest two mechanisms you might expect a programming language (like Java) to make available for the management of concurrent tasks (threads).

5 Problem 6. Answer the following questions about parameters. Parameters are part of definitions of methods and constructors, whereas arguments are part of the calling of a method or constructor. A. For a method or constructor call, what is the relationship between the order of the arguments and the order of the parameters? B. What must be true about the type of an argument and its corresponding parameter? C. What is the purpose of parameters? D. If a method or constructor has no parameters, then how does it get values to use in the computation of an expression?

6 Problem 7. Below you will find part of a definition for the class OperaTicket, a class that is designed to represent tickets to the opera. public class OperaTicket int rownumber; int seatnumber; double price; public Ticket(int rownumberargument, int seatnumberargument, double priceargument) rownumber = rownumberargument; seatnumber = seatnumberargument; price = priceargument; public double computegroupdiscountedprice() double groupdiscountrate = 0.93; return price * groupdiscountrate; public boolean isaisleseat() int rightaisleseatnumber; int leftaisleseatnumber = 1; if (rownumber < 10) rightaisleseatnumber = 8; else rightaisleseatnumber = 12; if ((seatnumber == leftaisleseatnumber) (seatnumber == rightaisleseatenumber)) return true; else return false; A. Draw a circle around any class (instance) variables in the description, and draw a rectangle around any local variables in the description. B. Finally, specify, in words, two major differences between class (instance) variables and local variables.

7 Problem 8. Here s the outline of a class that represents a BankAccount. BankAccounts, which are associated with an owner and given an ID, are associated with a balance and a counter of how many transactions have been performed on the account. A. Complete the alternate constructor B. Complete the handlewithdrawal method Note: If one overdraws his or her account while doing a withdrawal (if the balance goes less than 0), one s account is charged a fee of $ % of the transaction that caused the account be overdrawn. public class BankAccount private String accountowner; private int accountid; private double balance; private double numberofcompletedtransactions; public void handledeposit(double amounttodeposit) balance = balance + amounttodeposit; numberofcompletedtransactions = numberofcompletedtransactions + 1; //write an alternate constructor, add parameters if needed public BankAccount( ) // add instructions as appropriate // write a handlewithdrawal method public void handlewithdrawal(double amounttowithdraw)