Queens College, CUNY Department of Computer Science CS 212 – Object-Oriented Programming in Java -- Exam 1 – Practice B Last Name___________________________________ First Name __________________________ Seat______ Directions: Read the whole question before answering. Proper use of Java concepts is expected; minor syntax errors will be overlooked. 1. (25 points) Write a Java application that accepts one String parameter from a JOptionPane inputDialog and prints to a JOptionPane messageDialog the number times two digits in a row occur. For example: Input string: messageDialog says Testing 12 Two digits happen 1 time. Testing 123 Two digits happen 2 times. 123 Testing 12 23 234 Two digits happen 6 times. Hint: Recall that there is a method in the Character wrapper class: boolean Character.isDigit (char c) Continue the back of the page as needed CS 212 Exam 1 PRACTICE B Page 2 2. (25 points) Write a boolean method that will return true if the sum of the diagonal (upper-left to lower-right) of a two-dimension array is equal to the sum of a given row: diagonalEqualsRow ( int [][] myArray, int row) If the array is not a square matrix of the row number is out of bounds, throw an IllegalArgumentException with an appropriate message. For example: myArray1 1 3 5 7 9 2 3 4 6 8 0 1 5 1 3 4 5 2 7 8 7 6 3 2 9 myArray2 1 3 3 2 4 2 5 6 1 2 3 4 7 8 9 4 myArray3 1 3 5 6 7 0 8 7 4 3 myArray4 1 3 3 2 4 2 5 6 1 2 3 4 7 8 9 4 diagonalEqualsRow (myArray1, 0) returns true diagonalEqualsRow (myArray2, 2) returns true diagonalEqualsRow (myArray3, 0) throw an exception – not a square matrix diagonalEqualsRow (myArray1, 6) throw an exception – illegal row Continue the back of the page as needed CS 212 Exam 1 PRACTICE B Page 3 3. (25 points) Create the following class. Read the entire question first! Write a class Distance with the following specifications: Class variables: a private static integer called INCHES_IN_A_FOOT with a value 12; a private static float called FEET_IN_A_METER with a value of 0.3048f; Instance variables: Two integer instance variables: feet and inches; Constructors: a no argument constructor to initialize a Distance with zero feet, zero inches. a two argument constructor that will accept two positive integers and for feet and inches. An “IllegalArgumentException” is thrown if the number of inches is more than 11. Get/Set methods: get methods for the instance variables; set methods for instance variables. Public methods: 1. a method add() that adds another Distance object to itself. That is, w1 = new Distance(4,9); w2 = new Distance (3,6); w1.add(w2); // w1 becomes 8 feet, 3 inches 2. a method metricDistance() that will return (as a float) the number of meters in the distance represented by the object. That is, for w1 above, w1.metricDistance() returns 1.4478f Continue the back of the page as needed CS 212 Exam 1 PRACTICE B Page 4 4. (25 points) What will be printed by this program? public class Question4 { static String s1,s2,s3,s4; public static void main (String[] args){ s1 = new String("CAT"); s2 = new String("DOG"); s3 = new String("RAT"); animal(s1,s2); System.out.println(mixThem(s2,s3)); } //main private static void animal (String a1, String a2) { if(a1.equals(a2)) System.out.println(a1); else System.out.println(a2); } private static String mixThem (String b1, String b2){ String c1 = b1; b1 = b2; b2 = new String ("HAT"); System.out.println(b1); System.out.println(b2); System.out.println(c1); System.out.println(s2); return b2; } } //Question4 Answer here: