aps101s_2009_exam

APS101H1 FINAL EXAMINATION April-May 2009 Examine the following mystery method (hint: it has no compile errors!): [7 marks] public static void mystery1() { inti=0,j=3; for(i=0;i<5;i++) { // outer loop System.out.printin("Executing outer loop: " + i); while (j > i) { // middle loop ‘ j= for (int k = j; k < 6; k += 2) { // inner loop System.out.print("jis " +j+ ", kis" + k + ") } // end of inner loop Systei’n.out.println(); } // end of middle loop ji=3-i-1; } // end of outer loop System.out.printin("iis " + i+ ", jis " + i) What is the exact output that is produced by this method? Write it in the space below. Student #: Page 3 of 18 CONT'D...

APS5101H1 FINAL EXAMINATION April-May 2009 Question 3. [30 marks] The following is a different implementation of the Passport class that you wrote for Assignment 2. This time, an array is used to store the countries visited. Part (a) [2 marks] Complete the constructor. Do not add any more instance/static variables! public class Passport { private String name; /** The name of the passport owner. */ private String[][] visited; /** The countries visited by the owner of the passport. */ // The format of this variable is as follows: { {countryl, duration}, {country2, duration}, ...} /** A new passport with name n, and NO countries visited. Initialize both instance variables! */ public Passport(String n) { } // end of constructor Part (b) [28 marks] Complete the following 3 methods. Do not add any helper methods. /¥* Return the country that the owner of this passport has visited for the longest duration, or empty string ( countries, return the left-most country (i.e. the country that appears earliest in the array). */ ) if no countries have been visited; If there is a tie between two or more public String longestVisitedCountry() { //[6 marks] } // end of longestVisitedCountry method Student #4: Page 6 of 18 CONT'D...

APS101H1 FINAL EXAMINATION April-May 2009 Question 4. [26 marks] Assume that the following 2 classes exist. public class Building { private int x; // x-coordinate private int y; // y-coordinate public Building{int r, int c) { this.x =r; -~ this.y = ¢; } public String location{() { return "(" + x4+ ", " +y+ ") } } public class House extends Building { ~ /** Number of people living in the house. */ private int numResidents; public House(int x, int y) { super(x, y); this.numResidents = 5; } public int getNumResidents() { return this.numResidents; } } Write a class called City, with the following specifications: Variable Type Variable Description Building(l[] The City is represented by a grid of buildings. Method Method Description The constructor for this City. It takes one String argument, of the form: XY xy)Z&Xy):Z ... (xy):Z”" where X and Y specify the size of the city grid, the (x,y) pairs are the coordinates of buildings in the City, and Z indicates the type of building that is in that location: either “B” for a general Building, or “H” for a City(String) House. Ex. “55(0,4):B (1,2):H (12,0):H (-1,2):B (0,4):H” You can assume that this format will always be preserved, but you should not make any assumptions about the validity of the x and y values. In case of duplicate coordinates, only add the first entry. If no building or house is specified at a particular coordinate, leave that location null. getGrid() Returns the representation of this City (as a Building[][}). . Returns the population (number of residents) of this City (as an int). The getPopulation() L. Gy number of people living in general Buildings should be counted as 10. Compare this City to the given City. Do this by dividing the population of each City by its size (number of elements on its 2D grid). If this value is compareTo(City) . . L o A , ) bigger for this City, returns 1. If this value is bigger for the given City, returns -1. If this value is the same for both Cities, returns 0 (as an int). Student #: CONT'D... Page 9 of 18

APS101H1 FINAL EXAMINATION April-May 2009 Question 5. [24 marks] The following program encrypts words and stores the result in a file. Part (a) [10 marks] Complete the encrypt method. You will be marked on correctness and code readability, so you must write comments within the method. The encryption algorithm works by swapping consecutive pairs of letters. (i.e. swap the Ist letter with the 2nd, the 3rd with the 4th, etc.). Note: if the word has an odd number of letters, you must move the last letter to the beginning, BEFORE doing the swapping, and ignore the 2nd last letter (i.e. don't swap it). Ex. | (even): "abed" -> "badc". Ex. 2 (odd): "abcde" > "aecbd". public static String encrypt(String word) { /** Return the encrypted version of the given word. */ } // end of encrypt method Student #: Page 12 of 18 CONT'D...

APS101H1 FINAL EXAMINATION - April-May 2009 [Use the space below for rough work. This page will not be marked, unless you clearly indicate the part of your work that you want us to mark. Do NOT detach this page.] Student #: ‘ Page 15 of 18 : . CONT'D...

APS101H1 FINAL EXAMINATION April-May 2009 Short Java APL descriplions (everylhing is public) Integer: . static int parselnt(String s) // = s’s value, as an int Double: static double parseDouble(String s) // = s's value, as a double string: String substring(int i, int j) // = the letters from i (inclusive) to j (non-inclusive) String substring(int i) // = the letters from i (inclusive) to the end int indexOf(String s) // = the index of s in this String; -1 if s is not a substring int indexOf(String s, int i) // = index of s after index i (inclusive); -1 if s not found int compareTo(String s) // < 0, = 0, or > 0 depending on whether this < s, =5, or > s. int length() // = the number of characters in this String boolean equals(String s) // = this String has the same contents as s StringTokenizer: StringTokenizer(String s) // Create a tokenizer for s with delimiters " \t\n\r\f" StringTokenizer(String s, String d) // Create a tokenizer for s with delimiters ind’ StringTokenizer(String s, String d, true) //delimiters are also considered as tokens. boolean hasMoreTokens() // = whether this string tokenizer has more tokens String nextToken() // = the next token in this tokenizer's string int countTokens() // = the number of remaining tokens in this tokenizer's string File: File(String pathname) // Create a File linked with a file named f BufferedReader: : BufferedReader(Reader in) // Create a reader reading from ’'in’ String readLine() // Return the next line in the BufferedReader, or null if at end FileReader: FileReader(String f) // Create a Reader reading from a file named f FileReader(File f) // Create a Reader reading from a file f InputStreamReader: InputStreamReader(InputStream in) // Create a Reader reading from in FileOutputStream: (a subclass of OutputStream) FileOutputStream(File f) // Create an OutputStream writing to f FileOutputStream(String fn) // Create an OutputStream writing to a file named fn PrintStream: PrintStream(OutputStream out) // Create a print stream sending output to out print(String s) // Print s to the output printin(String s) // similar to above plus it terminates the line print(int i) // Print i to the output (similar methods exist for all primitive types) printIn(int i) // similar to above plus it terminates the line printin() // terminate the line System: static InputStream in // input from the keyboard _static PrintStream out // standard output stream Math: ) static double abs(double a) // = the absolute value of a * static double min(double a, double b) // = minimum of a and b static double max(double a, double b) // = maximum of a and b Stud_ent #: Page 18 of 18 END OF EXAMINATION