Name USC loginid e g ttrojan CS 455 Midterm Exam 1 Fall 2013 Bono Wednesday Oct 2 2013 There are 5 problems on the exam with 53 points total available There are 8 pages to the exam including this one make sure you have all of them If you need additional space to write any answers you may use the backs of exam pages just direct us to look there Note if you give multiple answers for a problem we will only grade the first one Avoid this issue by labeling and circling your final answers and crossing out any other answers you changed your mind about though it s fine if you show your work Put your name and USC loginid at the top of the exam Please read over the whole test before beginning Good luck value Problem 1 6 pts Problem 2 10 pts Problem 3 8 pts Problem 4 14 pts Problem 5 15 pts TOTAL 53 pts score Selected methods of Java Point class new Point x y Constructs point object with given x and y values new Point p2 Constructs point object that has the same value as point p2 p translate dx dy Changes x and y values of p by dx and dy respectively I e if p had coordinates x y it s new value is a point with coordinates x dx y dy Problem 1 6 pts Consider the following static method that is supposed to return a String describing the weather when given an outside temperature in Fahrenheit Approximately equivalent temperatures are also shown in Celsius for those of you who aren t used to Fahrenheit It doesn t always do the right thing public static String getWeather int temp if temp 90 weather boiling 90 is about 32 C if temp 90 temp 80 weather hot 80 is about 27 C if temp 80 temp 70 weather just right 70 is about 21 C if temp 70 temp 60 60 is about 16 C weather cool else weather cold return weather Do not modify the code Show two example data values and the result of calling the method on each of them the first one should be one where the existing method returns an incorrect weather description and a second one such that the method returns an accurate weather description temp return value of getWeather temp 1 wrong 2 right 2 Problem 2 10 pts Consider the following code fragment Note more about Point class on the front page of the exam Point p1 new Point 5 10 Point p2 new Point p1 Point p3 p2 p1 translate 3 7 p2 translate 3 7 p3 translate 3 7 System out println p1 p2 p3 Part A 5 In the space below draw a box and pointer diagram a k a memory diagram showing all object variables objects and their state as they have changed during the code sequence Part B 3 What is printed by the code For the purpose of this problem assume a Point is printed as follows x y Part C 2 How many Point objects are created by the code above 3 Problem 3 8 pts Consider the following new version of the remove method we discussed for the names class As before you may assume that the helper method lookupLoc returns the location of the value to remove or 1 if it wasn t found public class Names private String namesArr the capacity is namesArr length private int numNames private final static int NOT FOUND 1 not all of the Names class is shown here Removes target from names and returns true If target wasn t present in names returns false and no change made to names public boolean remove String target int loc lookupLoc target if loc NOT FOUND return false for int i numNames 1 i loc i namesArr i 1 namesArr i numNames return true Part A 3 Show an example target for which the method gives the wrong result and what that result is Hint it may be helpful to hand trace the code to find the bug Contents of namesArr and numNames before call to remove namesArr 0 1 Ann Bob 2 Carol 3 4 Don Ed numNames 5 a value of target b contents of namesArr and numNames after call to remove Part B 5 Fix the code above Do not rewrite the whole method but rather make your changes right into the code above using arrows to show where your code should be inserted crossing out code that you would get rid of etc 4 Problem 4 14 pts Complete the implementation of the class WordLengthFreq which computes the frequency of word lengths in a collection of Strings Here s an example of how we might use this class to compute the frequency of word lengths for all values from a file using input redirection to get the data from a file public static void main String args Scanner in new Scanner System in WordLengthFreq counter new WordLengthFreq while in hasNext String word in next counter countWordLength word counter printFrequencies Sample input and output for the program above Contents of the file the farmer in the dell the farmer in the dell heigh ho the merrio the farmer in the dell What gets printed by the program above Word Length Frequency count 2 21 4 3 37 7 4 16 3 5 5 1 6 21 4 Hints and simplifying assumptions you may make You may assume that no word will be greater than 80 characters long Use Math round double d to get the nearest int for percentage values You do not have to worry about the column formatting above you may print one space between a word length and its frequency Detailed descriptions of the methods appear with the class interface Turn the page for space for your answer includes the class interface for you 5 Problem 4 cont Computes the frequency of word lengths for a collection of strings public class WordLengthFreq Create an empty WordLengthFreq object i e 100 of word lengths are 0 because there are no words public WordLengthFreq Add this word to the collection for which we are computing the frequencies PRE 0 word length 80 public void countWordLength String word class definition continued next page 6 Problem 4 cont Print out a table of the various word lengths and their frequencies as percentages listed in increasing order by by word length Also shows number of occurrences for each of the lengths Lengths occurring with zero frequency are not shown If no words have been counted print No words given public void printFrequencies we wrote the code for the header line for you System out println Word Length Frequency count 7 Problem 5 15 pts Implement the static boolean method hasAlt which returns true iff the given array consists solely of alternately increasing and decreasing pairs of adjacent values For an array of zero or one elements hasAlt is true The examples with the annotations to the right should make it clear what we mean by alternating pairs arr return value of hasAlt arr Ex1 1 2 5 8 …