Exercices about collections

For all methods, you will write JUnit tests.

Exercice 1

Create a class representing a Time (in the form 'hour','minute', and ante/post meridiem).

public class Time {
	public int getHour() {
		
	}
	
	public int getMinutes() {
		
	}
	
	public boolean beforeMidday() {
		
	}
}

We decide that two Time are equals if all their attributes are equals
update the class, adding the correct equals and hashCode methods
Create a HashSet with a few Times in it, and check you can correctly find if it contains a given value
Same thing with a tree set

Now, suppose we want an Agenda class, which represent appointments. An appointment will have a Time, and a description. Two appointments can't be at the same time in the agenda. Choose the right class for implementation. Agenda interface:

public interface Agenda {
	void addAppointment(Time t, String description);
	String getAppointment(Time t);
	void removeAppointment(Time t);
	boolean hasAppointment(Time t);
	List listAppointments();
}

public class Appointment {
	private Time t;
	String description;
	// to complete...
		
	
}

Exercice 2

Question 1

We create a SocialUser class. Each SocialUser has a name, and a set of friends (who are themselves SocialUsers). Propose an implementation. It should have a addFriend() method. Note that we suppose that if x is a friend of y, then y is a friend of x.

Question 2

A relation is a friend, or a friend of a friend, etc... more precisely, friends are relations, and relations of friends are also relations. Try to use the following algorithm to implements a getRelation() method:

    e= current social user
	stack= empty stack
	seen= empty set
	
	push e.friends on stack
	add e to seen
	while stack is not empty:
		e1= stack.pop()
		if (seen does not contain e1) 
		    add e1 to seen
			push e1.friends on stack
		end if
	end while
	// now, seen contains all the relations of e.