Agfdhyk

It is an OOD question. Design a calendar.
The requirement are:

• add event


• delete an event


• get all events for a particular day

Justify the data structure and design test cases

I know that I need to provide the APIs like addEvent(), deleteEvent(), getEventByDay()

I stuck at the first API, add an event.
I have proposed two solutions, I just do not know which pattern is better and why.

version1:

public class Calender {

    // helper class

    public static class Event {

        String name;



        Event(String s) {

            name = s;

        }

    }



    Calender() {



    }



    // API

    public void addEvent(Event e) {

        // todo

    }



    // driver function

    public static void main(String args) {

        Calender calender = new Calender();



        Event event = new Event("event");

        calender.addEvent(event);

    }

}

version2:

public class Calender {

    int systemId;



    // helper class

    public static class Event {

        String name;



        Event(String s) {

            name = s;

        }

    }



    Calender() {



    }



    // API

    public int addEvent(String s) {

        Event event = new Event(s);

        systemId++;

        return systemId - 1; // after add an event, return the unique id for it

    }



    // driver function

    public static void main(String args) {

        Calender calender = new Calender();

        int id = calender.addEvent("a");

    }

}

The above class is not completed.
The major difference is that do we need to let the user create an Event then add this instance or just using existing API to create a event and get a unique id for this event?

I would keep both methods. Allow the user to either insert a new Event object or just pass the string and add it.

public class Calendar {

    public static class Event {

        String name;



        Event(String s) {

            name = s;

        }

    }



    Calendar() {

    }



    public void addEvent(Event e) {

        // todo

    }



    public int addEvent(String s) {

        Event event = new Event(s);

        systemId++;

        return systemId - 1; // after add an event, return the unique id for it

    }



}

That said, I would do the following:

• Remove the main from the Calendar class, it should be in a separate Application class for example, that would instantiate your calendar.


• Instead of returning the ID of the event when you add it, add a field id to your Event class, fill it with the new ID, and return the whole Event object.


• Maybe put the Event class in a separate file instead of having it in Calendar. It's arguable if it makes sense or not so that's left to your appreciation.

Beside that, you should store the list of events in your calendar, in order to be able to return the whole list of events or to delete one, as stated by the subject of your exercise.

Calendar and Event, as I identify, are two different, self contained entities.
Although an Event may be dependent on the Calendar object to store its date/time specific. They should be independent, and may not be wrapped within a Calendar API.

That being said, the version2 looks more promising, and scalable. Version2 gives you flexibility to modify the Event class to extend the capabilities, modify constructors, or add methods easily, without affecting Calendar .

For example, if you need to add the Event's venue along with its Name, you can simply modify Event's constructor. Or add another method inside the Event class. Leaving Calendar unaffected.

On a different design point, the Event class can also extend Calendar, if the Calendar use case is only specific to adding date/time capabilities to an Event.