boolean add(e e); // Makes the collection contain e. // Returns true if e not already there.

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1 1 1. (a) The Java collections classes includes the generic interface Collection<E> for collections with element type E, which the collection classes implement. This includes the following method: boolean add(e e); // Makes the collection contain e. // Returns true if e not already there. Is Collection<String> a Java subtype of Collection<Object>? Explain why or why not. Include an example showing how the the principle of substitutability applies in this case. (b) Consider the following Java code. public abstract class MyClass { public void setobject(object o); public Object getobject(); public class MySubclass extends MyClass { String obj; public void setobject(string s) { obj = s; public String getobject() { return obj; public static void main(string[] args) { MySubclass mysub = new MySubclass(); mysub.setobject("a STRING"); String gotten = mysub.getobject(); System.out.println(gotten); (i) What will happen when we compile and run this program? Explain.

2 2 (ii) Show how to fix this program so that it works as expected. Make only the minimal changes required, and explain your changes and why they are minimal. You only need to include the lines of code that need to be changed, and your explanation. 2. (a) Object-oriented programming is often considered fundamentally more intuitive than imperative programming. Explain why. (b) Briefly summarize the other main advantages of object-oriented programming compared to traditional imperative programming. (c) Explain the difference between an is-a and a has-a relationship. Include how each is most commonly implemented in an object-oriented program. (d) Give two examples of abstraction in programming. For each briefly say why it is useful. (3) (3)

3 3 3. (a) Give 3 important differences between Java and C++, and explain the practical consequences of each in terms of advantages and disadvantages. (b) Convert the following Java program to an equivalent C++ program, following the style in lectures. public abstract class MyClass { public void setstring(string s); public String getstring(); public class MySubclass extends MyClass { String str; public void setstring(string s) { str = s; public String getstring() { return str; public static void main(string[] args) { MySubclass mysub = new MySubclass(); mysub.setstring("a STRING"); String gotten = mysub.getstring(); System.out.println(gotten); (6)

4 4 4. (a) Consider the following Objective C code. #import <Foundation/NSObject.h> #import <Foundation/NSString.h> #import AddressCard: NSObject { NSString *name; NSString * ; - (AddressCard*) initwithname: (NSString*) n (NSString*) e; - (NSString*) name; - (NSString*) ; - (void) setname: (NSString*) n; - (void) set (NSString*) e; - (void) setname: (NSString*) n AddressCard - (AddressCard*) initwithname: (NSString*) n (NSString*) e { self = [super init]; if( self ) { [self setname: n]; [self set e]; return self; - (NSString*) name { return name; - (NSString*) { return ; - (void) setname: (NSString*) n { [n retain]; [name release]; name = n; - (void) set (NSString*) e { [e retain]; [ release]; = e; - (void) dealloc { [name release]; [ release]; [super (i) Explain broadly what this code does.

5 5 (ii) Explain the need for each use of retain and release, and why they must appear in the order that they do. (iii) If you were writing this code in Java, is there something similar to retain and release that you would use? If so what? If not, why aren t they needed? (b) Give 3 important differences between Java and Objective C, and explain the practical consequences of each in terms of advantages and disadvantages.