page 1 of 14 THE UNIVERSITY OF MANITOBA FINAL EXAMINATION COURSE CODE: COMP 2150 DATE: April 25, 2019 TITLE: Object Orientation TIME: 9:00 AM INSTRUCTORS: Boyer (A01) / Domaratzki (A02) DURATION: 3 HOURS Academic Integrity Contract I understand that cheating is a serious offence. integrity. Any Student who engages in Academic Misconduct in relation to a University Matter will be subject to discipline (2.4 - Student Academic Misconduct Procedure). Student Signature:______________________________ Instructions 1. Answer all questions on the paper Crowdmark will only show answers written on the page. 2. No aids permitted (e.g., no calculators, no books); turn cell phones off, and keep them out of sight. page 2 of 14 Section A: Predict the output (10x1 mark) For each of the following code blocks, write the output on the right-hand side. The examples are from Java (first 3), Ruby (middle 3) and C++ (last 4). You can assume that any namespace and include statements are present in the code to ensure they do not cause any errors. You may assume java classes are in appropriately named files. If the code otherwise does not compile, indicate this and the specific reason why. public class A { public static void main (String[] args) { T a = new U(); System.out.println( a.x() ) ; } } class T { public String x() { return "b"; } } class U extends T { public String x() { return "a"; } } public class B { public static void main (String[] args) { T aa = new U(); T bb = new U(); System.out.println( aa.x( bb ) ) ; } } class T { public String x(T y) { return "b"; } } class U extends T { public String x(U y) { return "a"; } } public class C { public static void main (String[] args) { Abs c = new conc(); c.something(); } } abstract class Abs { public abstract void nothing(); public abstract void something(); } class Conc extends Abs { public void something() { System.out.println("aa"); } } class One def info end end class Two < One def info end end x = Two.new puts(x.instance_of?(One)) puts(x.respond_to?(:info)) page 3 of 14 class A # semicolons used to save space only def A.new(*args) if self == A puts('1') else puts('2'); super end end def initialize() puts('3'); end end class B < A def initialize() puts('4'); end end b = B.new puts('5') module M # semicolons used to save space only def modif (y) y-1 ; end def inh puts 'AA'; end end class A def inh puts 'BB'; end end class B < A def modif (x) x+1; end include M def do inh if modif(3) == 2 puts 'CC' else puts 'DD' end end end b = B.new b.do class MyClass { private: string info; public: MyClass() { info = "S";} MyClass (const MyClass& src) { info = src.info + "C"; } MyClass& operator= ( MyClass& right) { info = right.info + "A"; } void getInfo() { cout << info << endl; } }; int main(void) { MyClass first; MyClass second (first); MyClass third = second; first = third; third.getInfo(); first.getInfo(); return 0; } page 4 of 14 class A { protected: int y; public: A () { y = 2; } virtual int method() { return y;} }; class B: public A { public: B() { y = 3; } int method() { return y*y;} }; int main() { B b; A a = b; cout << a.method() << b.method(); return 0; } class Gen1 { public: Gen1() {} int f1() { return 1; } int f2() { return 0; } }; class Gen2 : private Gen1 { public: Gen2() {} int f1() { return 1+Gen1::f1(); } }; class Gen3: protected Gen2 { public: Gen3() {} int m1() { return 1+this->f1(); } }; int main() { Gen3* g3 = new Gen3(); cout << g3->m1()<< " " << g3->f2() << endl; } class Parent { protected: string info; public: }; class Child: public Parent { public: Child() }; int main() { Parent* var = new Child(); cout << var->method(); return 0; } page 5 of 14 Section B: Short Answer (20 marks) 1. [2 marks] What two components are necessary in an OO language to allow polymorphism? ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 2. [2 marks] Consider the following two C++ class Parent1 and Parent2: class Parent1 { public: string fun1() { return "a"; } string fun2() { return "b"; } }; class Parent2 { public: string fun1() { return "c"; } string fun2() { return "d"; } }; You may assume that all the required includes and namespace declarations have been made. Write a class Child that inherits from both Parent1 and Parent2 and has a method combo() that returns a string. The method combo() should or variables in the Child class and must use the methods defined in Parent1 and Parent2. The methods of Parent1 and Parent2 must not be callable when using a Child object. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 3. [2 marks] Suppose that Child is a subclass of Parent in C++ and we have the following line of code: Parent* obj = new Child(); After this line, what code do we need to write to be allow obj to safely access the methods that are defined as public in Child but not defined in Parent? Write the line(s) of code only. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ page 6 of 14 4. [2 marks] Using an example, show the relationships between two classes described by specialization. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 5. [2 marks] Using an example, show the relationships between two classes described by containment. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 6. [2 marks] Describe how - differ in Java. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 7. [2 marks] In Ruby, show how private and protected are different through an example. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 8. [2 marks] List the four methods that are important under OCCF. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 9. [2 marks] Describe how a class variable (@@var, not a class instance variable) behaves in ruby in a class and its subclasses. ___________________________________________________________________ ___________________________________________________________________ page 7 of 14 ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 10. [2 marks] In Ruby, describe what happens when two methods with the same name are defined in the same class. How does Ruby allow a programmer to deal with this situation? ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ Section C: Ruby Programming (10 marks) Consider the following iterator class from Assignment 3, written in Java: public class Iter implements JSONIter { private Node curr; public Iter (Node start) { curr = start; } public boolean hasNext() { return (curr != null); } public Value getNext() { if (curr != null) { Value li = curr.getItem(); curr = curr.getNext(); return li; } else { throw new NoSuchElementException("no more elements"); } } } The Iter class uses a standard Node class, with getNext() and getItem() methods. It assumes the Node class holds values that satisfy the Value Interface: public interface Value { public String toString(); } Implement the Iter class and an abstract class Value in Ruby. Make sure you use appropriate encapsulation features. You do not need to write the Node class but may assume it has accessors for the data members (attributes) called item and next. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ page 8 of 14 ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ Section D: Java Programming (10 marks) Consider a category of numbers T that have four operations defined on them: next number in the category. The next operation on an object of type T takes no parameters and returns an object of the same type T. This operation represents the next object of the same type according to an ordering of the set T. divisible sible by another object. The divisible method takes a parameter p of type T and determines if the object is divisible by p. It returns a boolean. equals s if two T objects are equal. The equals method takes a single parameter of type of type T and returns a boolean that gives if the two objects represent the same element of T. first the unique object of type T set, for a definition of first that depends on T. The method always returns the same result. As an example, if T is the category of all integers, then the next operation for an object n would return n+1, and divisible would be normal integer divisibility (i.e., in pseudocode, 10.divisible(4) would return false and 10.divisible(5) would return true.) The first method should always return the number 1. If a category of objects T has these four operations then we call it PrimeTestable. a) Write a Java interface called PrimeTestable that captures the specifications for the four operations described above. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ b) Write a Java class called IntTestable that satisfies the PrimeTestable interface. The class should have a single field, of type integer. The methods that implement the interface should use the standard definitions for divisibility, next and equals. As mentioned above, first should always return an IntTestable object with value 1. The constructor for IntTestable should take a single int parameter. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ page 9 of 14 ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ c) Write a Java class called Prime that has one static method called primeTest. The primeTest method should take a single parameter of type PrimeTestable and returns a boolean according to whether the number is prime or not. To test whether a PrimeTestable x is prime or not, look at all the numbers between (but not including) x and check if any of them divide x. PrimeTestable t1 = new IntTestable(25); PrimeTestable t2 = new IntTestable(23); System.out.println(Prime.primeTest(t1)); System.out.println(Prime.primeTest(t2)); ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ page 10 of 14 Section E: C++ Programming (15 marks) In this question, you will write code to support a smart home. Our smart home will have three different types of smart devices in it: A single thermostat for the house, which controls the temperature for the house. Zero or more lightswitches, which have a location and a status (on or off). A single controller, which can control all of the lightswitches and the thermostat for the house. There is one controller per house. The code below is organized into .h and .cpp files for each of the required classes (Thermostat, Lightswitch and Controller) as well as the abstract superclass of Thermostat and Lightswitch (called Thing). Additionally, the .h files for the Node and List classes (similar to what was shown in class) and the Iterator class (similar to the Java code provided in Section C) are provided. The .cpp files for these classes are not provided here, but you may assume that you have them and that they work. You are only required to provide forward references/includes for these .h files. Instructions and notes: Fill in all underlined areas in all .h files: these are either includes or forward references. For all Lightswitches and Thermostats: o Each device needs to be aware of its controller (to be able to call methods from the controller). For the Lightswitch class: o When created, all lightswitches are off. o Each lightswitch has a location, which is typically a room in the house. It is stored as a string. o Each lightswitch has a toggle function, which switches the light from on to off (or vice versa). For the Thermostat class: o When created, a thermostat is set to 20 degrees. o The method setTemperature sets the temperature on the thermostat. For the Controller class: o There are two methods, addLightSwitch and setThermostat, to add devices to the house. addLightswitch adds a new lightswitch (in addition to the others already added). setThermostat sets the only thermostat in the house (overwriting the previous one if applicable). o The method setHome() turns all the lights on and sets the temperature to 20 degrees. o The method setAway() turns all the lights off and sets the temperature to 16 degrees. For this page, fill in the underlined areas ONLY. You do not have to provide .cpp files for ANY of these classes. Node.h List.h Iterator.h _____________________ // for Thing ________________________ // for Node ________________________// for Thing _____________________// for Iterator ______________________ // for Node ______________________// for Thing page 11 of 14 Thing Lightswitch for Controller class for Thing class page 12 of 14 Controller Thermostat Controller.h for List for Thermostat for Lightswitch Thermostat.h for Thing Controller.cpp Thermostat.cpp page 13 of 14 If necessary, use this page for extra answers. Indicate clearly which question you are answering here: ____________________ page 14 of 14 If necessary, use this page for extra answers. Indicate clearly which question you are answering here: ____________________
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