Class Design of a meeting scheduler using OO principles - oop

Question

What would be the sample class design of Outlook like meeting scheduler?
This should help you to schedule a meeting with the rest of the invitees and book a room as we do in offices.
Few things I omit purposely,i.e checking meeting room availability, person availability at looking his/her calendar.
Here is my approach to this. I would love to know what improvements can be there and mistakes have done in the process.
class Person{
String name;
Email emailId;
}
class Organizer{
Person organizer; //using composite here
public void Organizer(Person p){
this.organizer = p;
}
private boolean scheduleMeeting(){
Meeting m = Meeting.getInstance();
sendInvites(m);
}
private void sendInvites(Meeting m){
for(Person p : m.inviteesList){
send(p.emailId, m);
}
}
}
class Meeting{
private String agenda;
private String bodyMessage;
private String location;
private TimeFrame time;
private ArrayList<Parent> inviteesList;
private Meeting(){}
public static Meeting getInstance(){
Meeting meet = new Meeting();
agenda = addLocation();
bodyMessage = addBody();
location = addLocation();
time = addTime();
addInvitees();
return meet;
}
}
class TimeFrame{
Time startTime;
Time endTime;
}
Edit - Update on the above
https://codeshare.io/5e4vNx
Any help on this would be appreciated.

Answer 1

Despite the oft-cited "favour composition over inheritance", Organizer is a valid extension of the Person class, provided it has additional responsibilites not fulfilled by the Person class. However, it is not its responsibility to create meetings and to send invites; that is the responsibility of a Scheduler.
Also, you might not need a separate Organizer class because it could simply be the role played on the Person side of a Meeting--Person relationship, as below.
* [organizer] 1
Meeting -----------------> Person
| ^ *
| | [invitees]
| |
+--------------------------+
Now, this is a nit-pick: I think Period is a better name than TimeFrame.
Also, I like your use of an abstract data type Email instead of a simple String; it helps enforce strict typing.
Without knowing the requirements of your system, I would go with something like the following.
class EmailAddress {
String value;
public EmailAddress(String value) {
// TODO validate email address here
this.value = value;
}
public String get() {
return value;
}
}
class Person {
String name;
EmailAddress emailAddress;
public Person(String name, EmailAddress emailAddress) {
this.name = name;
this.emailAddress = emailAddress;
}
}
class Meeting {
Person organizer;
Person[] invitees;
Period period;
String description;
public Meeting(Person organizer, Person[] invitees, Period period, String description) {
this.organizer = organizer;
this.invitees = invitees;
this.period = period;
this.description = description;
}
}
class Period {
Date start;
Date end;
public Period(Date start, Date end) {
this.start = start;
this.end = end;
}
}
class SchedulerFacade {
public Meeting schedule(EmailAddress organizerEmailAddress, EmailAddress[] inviteesEmailAddresses, Period period, String description) {
// TODO validate organizer and invitees
// TODO create Person instances for organizer and invitees
// TODO check for schedule conflict, etc.
Meeting meeting = new Meeting(organizer, invitees, period, description);
// TODO save meeting
return meeting
}
}