CS 177 Spring 2009 Exam I

Transcription

1 CS 177 Spring 2009 Exam I There are 40 multiple choice questions. Each one is worth 2.5 points. The total score for the exam is 100. Answer the multiple choice questions on the bubble sheet given. Fill in the Instructor, Course, Signature, Test, and Date blanks. For Instructor put your RECITATION INSTRUCTOR S LAST NAME GIVEN BELOW. For Course put CS 177. For Test put exam1. Fill in the bubbles that correspond to your name, section and Student ID in the bubble sheet. For your section number, use the SECTION NUMBER of your recitation section. Consult the following list: 001 FRI 07:30 HAAS G066 Pelin Angin 002 FRI 08:30 HAAS G066 Jackie Soenneker 003 FRI 10:30 HAAS G066 Ryan Phelps 004 FRI 02:30 HAAS G066 Yao Zhu 005 FRI 03:30 HAAS G066 Younsun Cho 006 FRI 12:30 HAAS G066 Tion Thomas 016 FRI 11:30 REC 117 Yi-Liu Chao For your student ID, use the 10 digit ID number on your student ID card. DO NOT USE YOUR SOCIAL SECURITY NUMBER! Exams without names will be graded as zero. Only the answers on the bubble sheet will be counted. The questions will be discarded. Recitation Section Number Recitation TA s Name Student Last Name Student First Name

2 Multiple Choice Questions (2.5 points each): 1. Examine the following fragment of code: if ( x < 10 ) if ( y > 5 ) System.out.println("non-stop"); else if ( y > 2 ) System.out.println("hip"); else System.out.println("hop"); If the output of this fragment is hip, what is the most precise statement you can make about the values of x and y? (a) x is smaller than 10 and y is 2 or smaller. (b) x is smaller than 10 and y is bigger than 5. (c) x is smaller than 10 and y can only be 3, 4, or 5. (d) x is bigger than 10 and no information about the value of y is known. 2. What would be output to the console after the following piece of Java code is executed? boolean test1 = true; boolean test2 = false; boolean test3 =!(test1 test2) && test1; System.out.print("The answer is "); System.out.print(test3); (a) The answer is 0 (b) The answer is true (c) The answer is false (d) The answer is 3. Which of the following best describes the function of the == operator in Java? (a) It assigns the left operand the same value as the right operand. (b) It compares two operands to determine if they are equal and gives back a boolean. (c) It changes the right operand s data type to be equal to that of the left operand. (d) It compares two operands to determine if they are equal and gives back an int. 4. What is the purpose of an if-statement in Java? (a) An if-statement allows you to assign a value to a variable. (b) An if-statement allows you to print data onto the screen. (c) An if-statement allows you to execute a block of code if a condition is true. (d) An if-statement allows you to execute a block of code repeatedly. 1

3 5. Consider the following two code samples: Sample 1: int x = 49; double y = Math.sqrt(x); Sample 2: double x = 49.0; int y = Math.sqrt(x); Sample 1 is valid Java code while Sample 2 results in a compile time error. Why? (a) Sample 2 does not result in a compile time error. (b) The Math.sqrt() method can take an int as input but not a double. (c) An int can be promoted to a double, but turning a double into an int loses precision. (d) The square root of 49 is a whole number, but the square root of 49.0 is a floating point number. 6. Consider the following code fragment: int a = 32; double b = 5; System.out.println("a + b is " + a + b); Which of the following best explains what would result from running the code above? (a) The output would read a + b is since System.out.println() will not know how to process a and b. (b) The output would read a + b is 37.0 since the addition will happen before the data is concatenated into a String. (c) The output would read a + bis325.0 since the + operator automatically converts ints and doublestostrings. (d) There will be a compiler error since a and b do not have the Stringdata type. 7. What is the data type of the variable flag if the following statement is valid? if (flag (i <= 10)) i++; (a) boolean (b) String (c) int (d) double 2

4 8. What does the following program print out? public static void main(string args[]) int i = 0; int j = 1; if (i = j) System.out.println(i); else System.out.println(j); (a) 1 (b) 2 (c) This program does not compile correctly. (d) 0 9. What does the following program print out? public static void main(string args[]) String str1 = "home"; String str2 = "chromosome"; String result = "not sure"; if (str1.compareto(str2) < 0) result = "smaller"; else result = "bigger"; System.out.println("I am " + result + "."); (a) I am smaller. (b) I am result. (c) I am not sure. (d) I am bigger. 10. What value does the variable z have as a result of executing the following program segment? int x = 4; double y = 10.8; double z = (double)(x * (int) y); (a) 43.2 (b) 43 (c) These statements cause a compile-time error. (d)

5 11. What is the output of the following program? public static void main(string args[]) int i = 10; while(i > 0) i--; if (i % 2 == 0) System.out.print(i + " "); (a) This program does not compile correctly. (b) (c) (d) Given a program named Expense which takes three integer arguments (tuition, housing, food), which of the following statements assigns the value of the housing argument to the variable h when the program is executed using the command: java Expense (Note that the value of the housing argument here is 600 and the command line arguments are stored into the args variable, as usual.) (a) int h = Integer.parseInt(args[1]); (b) int h = args[2]; (c) int h = Integer.parseInt(args[2]); (d) int h = Double.parseDouble(args[0]); 13. What is the output of the following program segment? int x; double y = 3.7; double z = 3.2; int t = (int)math.round(y); int u = (int)math.round(t + z); System.out.println(u); (a) 8 (b) 7 (c) 6.9 (d) 6 4

6 14. Which of the following should we assign to the String variable mystring so that mystring.charat(2) gives the character n? (a) "liquidity" (b) "inflation" (c) "management" (d) "demand" 15. What is the output of the following program segment? String str = "Happy Lunar New Year"; int index1 = str.indexof("l"); int index2 = str.length(); int index3 = str.indexof(" "); String substr = str.substring(index1, index2); System.out.println(substr); (a) Happy New Year (b) Lunar (c) Happy Lunar New Year (d) Lunar New Year 16. Which of the following Java statements produces this output: The second word is "Lunar" (a) System.out.println("\"The second word is Lunar\""); (b) System.out.println("The second word is "Lunar""); (c) System.out.println(\"The second word is "Lunar"\"); (d) System.out.println("The second word is \"Lunar\""); 17. Which command will run the program Generic from the command line without causing an error? public class Generic public static void main(string[] args) int a = Integer.parseInt(args[0]); int b = Integer.parseInt(args[1]); System.out.println(a + b); (a) java Generic 3 hat (b) java Generic 23 6 (c) java Generic (d) java Generic 7 5

7 18. Command line arguments always have what data type? (a) int (b) String (c) boolean (d) float 19. Imagine that you want to declare a variable of type double to store the exchange rate between dollars and euros. Which of the following is not a legal declaration for such a variable? (a) double dollarstoeuros; (b) double DOLLARS_TO_EUROS; (c) double dollars2euros; (d) double dollars to euros; 20. Use the Buggy class given below for both questions 20 and 21. When Buggy.java is compiled, two errors will be found on the line where sum is declared and initialized. What causes these errors? public class Buggy public static void main(string[] args) int var1; int var2; var1 = 3 * Double.parseDouble(args[0]); double sum = Var1 + var2; System.out.println("The sum is: " + sum); (a) var1 has not been initialized and sum is misspelled. (b) var2 has not been initialized and var1 is misspelled. (c) An addition cannot be performed in the same statement declares a variable, and var1 is misspelled. (d) var2 has not been initialized and an int value cannot be stored in a double variable. 21. There is also another error in the Buggy class defined in the previous question. What is it? (a) A double value cannot be stored into the int variable var1. (b) The parsedouble() method cannot be used on a String. (c) An int value cannot be stored into the double variable sum. (d) A String and a double cannot be concatenated in the print statement. 6

8 22. Which of the following is not true regarding debugging in Java? (a) The Java compiler will always catch every problem in a program. (b) The act of fixing one error may cause the compiler to catch new errors that it didn t find before. (c) The compiler s error messages indicate the approximate line in the program on which each error occurs. (d) The Java compiler will catch and give messages about several different types of errors. 23. How many lines will the following program print? public class WhileLoop1 public static void main(string [] args) int i = 3; while ( i < 15 ) System.out.println("Hello " + i); i += 3; (a) 14 (b) 5 (c) 4 (d) What is the value of variable i at the end of this program? public class WhileLoop2 public static void main(string [] args) int i = 0; while ( i <= 20 ) i = 2 * i; (a) 22 (b) 20 (c) The program never stops. (d) 32 7

9 25. Use the WhileLoop3 class given below for both questions 25 and 26. What is the value of variable a at the end of this program? public class WhileLoop3 public static void main(string [] args) int i = 0; int a = 1; double b = 1; while ( i < 5 ) a = (int)(a + 1.5); b = (double)(b + 1.5); i++; (a) 8.5 (b) The program never stops. (c) 6 (d) Following the previous question, what is the value of variable b at the end of the program? (a) 7 (b) 8.5 (c) 6.5 (d) The program never stops. 27. What is the purpose of a while-loop in Java? (a) In practice, while-loops are never used in Java programs because of the risk of infinite loops. (b) A while-loop is used to repeatedly execute a series of statements as long as a condition is true. (c) A while-loop can be used in place of a switch block. (d) A while-loop is used to choose between two different options. 28. What type of error can occur when running the javac command? (a) Run-time error (b) Catastrophic error (c) Logic error (d) Compile-time error 8

10 29. Consider the following fragment of code: while ( i < 5 ) i++; Assume that i is a properly declared variable of type int. What is the smallest number of times the body of the while-loop will be executed? (a) 5 (b) 1 (c) 4 (d) Which of the following sequences best describes the process of developing a Java program? (a) compile code execute code edit code (b) edit code compile code execute code (c) compile code edit code execute code (d) edit code execute code compile code 31. What command would you use to compile a file called Burninator.java? (a) javac Burninator.java (b) javac Burninator (c) java Burninator (d) java Burninator.java 32. What does the following Java code print out when run with this command: java Hello Bertie public class Hello public static void main(string[] args) System.out.print("What ho, "); System.out.print(args[0]); System.out.println("!"); (a) What ho, args[0]! (b) What ho, Bertie! (c) What ho, Bertie! (d) What ho, Bertie! 9

11 33. What does the following Java code print out? public class Program public static void main(string[] args) //System.out.print("All your base "); System.out.println("are belong to us. "); /* System.out.println("You know what you doing."); */ (a) All your base are belong to us. You know what you doing. (b) are belong to us. (c) All your base are belong to us. (d) are belong to us. You know what you doing. 34. How many lines of text does the following Java program output? public class Program public static void main(string[] args) System.out.print("Waka waka bang splat "); System.out.println("tick tick hash,"); System.out.println("Caret quote backtick dollar dollar dash,"); System.out.print("Bang splat equal at "); System.out.println(dollar underscore,"); System.out.print("Percent splat "); System.out.print("waka waka "); System.out.println("tilde number four,"); System.out.println("Ampersand bracket bracket dot dot slash,"); System.out.println("Vertical bar curly bracket comma comma CRASH."); (a) 6 (b) 8 (c) 7 (d) 5 10

12 35. What is the output for the following fragment of code? int value = 2; switch( value ) case 1: System.out.println("Gold"); break; case 2: System.out.println("Silver"); case 3: System.out.println("Bronze"); break; default: System.out.println("Invalid Medal"); (a) Silver Bronze Invalid Medal (b) Silver (c) Gold (d) Silver Bronze 36. How do you increase the value of an intvariable named j by five? (a) j = j + 5; (b) 5 += j; (c) j := j + 5; (d) 5 + j = j; 37. What value is output for k? class Remainder public static void main (String args[]) int i = 10; int j = 3; int k = (i % j) + i * j; System.out.println("k is " + k); (a) 31 (b) 33 (c) 1 (d) 3 11

13 38. Which of the following will always give the same result as the expression below?!(!x!y ) (a)!(!x &&!y) (b) x && y (c)!x &&!y (d) x y 39. What is the value of the statement (int)(math.round(2.718) * 0.3)? (a) 3 (b) 2 (c) 1 (d) What is the output of the following fragment of code? int dayofmonth = 30; String number = "17700"; System.out.println(number.length()*dayOfMonth); (a) 30 (b) 150 (c) (d) 5 12