CSE142 Midterm Winter 2011 Name of Student_______________________________________________________________ Section (e.g., AA)___________________ TA_____________________________________ This exam is divided into nine questions with the following points: # Problem Area Points Score --------------------------------------------- 1 Expressions 10 _____ 2 Parameter Mystery 12 _____ 3 If/Else Simulation 12 _____ 4 While Loop Simulation 12 _____ 5 Assertions 15 _____ 6 Programming 15 _____ 7 Programming 15 _____ 8 Programming 9 _____ 9 Bonus 1 _____ ---------------------------- Total 100 _____ This is a closed-book/closed-note exam. You are allowed to have one hand-written index card up to 5" x 8". Space is provided for your answers. There is a "cheat sheet" at the end that you can use as scratch paper or to write answers. You are not allowed to access any other paper during the exam (not even scratch paper). Use the backs of the pages of this test if necessary. Anyone caught with extra paper will lose at least 10 points. The exam is not graded on style and you do not need to include comments, although you are limited to the constructs included in chapters 1 through 5 of the textbook. You are allowed to abbreviate "Always", "Never," and "Sometimes" as "A", "N", and "S" for the assertions question, but you should otherwise NOT use any abbreviations on the exam. You are NOT to use any electronic devices while taking the test, including calculators. Anyone caught using an electronic device will receive a 10 point penalty. Do not begin work on this exam until instructed to do so. Any student who starts early or who continues to work after time is called will receive a 10 point penalty. If you finish the exam early, please hand your exam to the instructor and exit quietly. 1. Expressions, 10 points. For each expression in the left-hand column, indicate its value in the right-hand column. Be sure to list a constant of appropriate type (e.g., 7.0 rather than 7 for a double, Strings in quotes). Expression Value 13 + 2 * 5 / 3 ________________ 2.5 * 2 * 5 / 10 + 1.5 ________________ 85 % 10 + 4 % 10 - 17 % 3 ________________ 2 + 3 + "." + (3 + 4) + 2 * 3 ________________ 482 / 10 / 5 / 2.0 * 2 + 14 / 5 ________________ 2. Parameter Mystery, 12 points. Consider the following program. public class Mystery { public static void main(String[] args) { String john = "skip"; String mary = "george"; String george = "mary"; String fun = "drive"; statement(mary, john, fun); statement(fun, "george", "work"); statement(george, mary, john); statement(george, "john", "dance"); } public static void statement(String mary, String john, String fun) { System.out.println(john + " likes to " + fun + " with " + mary); } } List below the output produced by this program. 3. If/Else Simulation, 12 points. Consider the following method. public static void ifElseMystery(int a, int b) { if (a == b) { b--; } else if (a < b) { a++; } else { b = b + 5; } if (a == b) { a = a + 2; } System.out.println(a + " " + b); } For each call below, indicate what output is produced. Method Call Output Produced ifElseMystery(14, 14); _______________ ifElseMystery(4, 5); _______________ ifElseMystery(10, 5); _______________ ifElseMystery(2, 8); _______________ 4. While Loop Simulation, 12 points. Consider the following method: public static void mystery(int y) { int x = 0; int z = 0; while (y > 0) { x++; z = z + y % 10; y = y / 10; } System.out.println(x + " " + z); } For each call below, indicate what output is produced. Method Call Output Produced mystery(8); _______________ mystery(32); _______________ mystery(184); _______________ mystery(8239); _______________ 5. Assertions, 15 points. You will identify various assertions as being either always true, never true or sometimes true/sometimes false at various points in program execution. The comments in the method below indicate the points of interest. public static int mystery(Scanner console) { int prev = 0; int count = 0; int next = console.nextInt(); // Point A while (next != 0) { // Point B if (next == prev) { // Point C count++; } prev = next; next = console.nextInt(); // Point D } // Point E return count; } Fill in the table below with the words ALWAYS, NEVER or SOMETIMES. next == 0 prev == 0 next == prev +---------------------+---------------------+---------------------+ Point A | | | | +---------------------+---------------------+---------------------+ Point B | | | | +---------------------+---------------------+---------------------+ Point C | | | | +---------------------+---------------------+---------------------+ Point D | | | | +---------------------+---------------------+---------------------+ Point E | | | | +---------------------+---------------------+---------------------+ 6. Programming, 15 points. Write a method called numUnique that takes three integers as parameters and that returns the number of unique integers among the three. For example, if the following call is made: numUnique(18, 3, 4) the method should return 3 because the parameters represent 3 different numbers (the values 18, 3 and 4). By contrast, the following call: numUnique(6, 6, 6) would return 1 because there is only 1 unique number among the three parameters (the value 6). The values passed to your method might appear in any order whatsoever, so you cannot assume that duplicate values would appear together. For example, if the following call is made: numUnique(7, 31, 7) the method should return 2 because there are 2 unique numbers among the parameters (the values 7 and 31). 7. Programming, 15 points. Write a method called printNumbers that takes a Random object as a parameter and that prints a list of randomly generated numbers ranging from 1 to 50 inclusive (each number being equally likely). The list should be surrounded by square brackets and the numbers should be separated by commas. The method should randomly generate numbers until it generates one that ends in 5. A typical call would look like this: Random r = new Random(); printNumbers(r); The method might fairly quickly generate a number ending in 5: [43, 34, 27, 2, 2, 25] Or it might take a while to get to a number ending in 5: [23, 8, 13, 1, 37, 37, 9, 34, 23, 34, 4, 9, 16, 44, 49, 43, 49, 3, 45] It is also possible that it will immediately generate a number ending in 5: [35] You must exactly reproduce the format of these examples. 8. Programming, 9 points. Write a method called numWords that takes a String as a parameter and that returns the number of words in the String. By definition, words are separated by one or more spaces. The table below shows several sample calls and the value that should be returned. Method Call Value Returned ---------------------------------------------------- -------------- numWords("how many words here?") 4 numWords("to be or not to be, that is the question") 10 numWords(" how about merry-go-round ") 3 numWords(" !&$%--$$!!*() foo_bar_baz ") 2 numWords("x") 1 numWords(" ") 0 numWords("") 0 Notice that words can contain punctuation marks. Any non-empty sequence of non-space characters can be a word. Also notice that there might be spaces at the beginning or end of the String. You may not construct any other objects to solve this problem (e.g., you can't use a Scanner or tokenizer). You may assume that the String has no other whitespace characters such as tabs or newline characters. Your method can pay attention just to spaces to decide how many words there are. 9. Bonus, 1 point. Please indicate in the box below the score you expect to receive on this midterm. Please give us your best estimate. Any number between 0 and 101 will receive the bonus point. +---------+ I expect to get a score of | | on this test +---------+ CSE142 Midterm Cheat Sheet Math Method Description -------------------------------------- Math.abs(n) absolute value of n Math.max(x, y) maximum of x and y Math.min(x, y) minimum of x and y String Method Description ----------------------------------------------------------------------------- charAt(index) character at a specific index indexOf(text) index of a particular string (-1 if not found) length() number of characters in string substring(start, stop) characters from start (inclusive) to stop (exclusive) substring(start) characters from start to end of string toLowerCase() lowercase version of string toUpperCase() uppercase version of string Syntax Examples: for (int i = 1; i <= n; i++) { System.out.println("****"); } if (n < 0) { System.out.println("negative"); } if (n < 0) { System.out.println("negative"); } else { System.out.println("not negative"); } while (n < 200) { n = n * 2; }