Object Oriented Programming Course Homework - VideosDB

November 2020

Dimitrie David 323CA

Info

https://ocw.cs.pub.ro/courses/poo-ca-cd/teme/tema

About my implementation

Models

I started by creating my own models:

• Show - abstract class with common methods & fields for both movies and serials (e.g. title, year), but also abstract methods that differ for movies and serials (e.g. the rating system).
  • Movie - final class
  • Serial - final class
• User - final class
• Actor - final class
• Action - final class

Main

I wanted my main function to look very clean. Because of this, I created my Database and ActionWorker classes. In main -> execute I initialize a new empty Database (DB is Singleton) and populate it with the Input object. After that, I initialize a new ActionWorker object and then I execute all the actions, updating arrayResult.

Database

I decided to store all my input data in a database-like class called Database.

This has a method populate, that takes an Input object and parses it into private arrays of each model enumerated above. In this parsing, I also count the number of show favorites count and show view count.

In the Database class, I also implemented some helper methods like getUserByUsername or getShowsByGenre.

ActionWorker

ActionWorker is a class that actually executes all the actions and update the result array. Here, the first action type switch appears. (comparing action_type) Based on the action type, a new class is created (Command, Query or Recommendation). All of these classes take the current action as parameter in their constructors, and they get the database instance.

ActionCommon

This class is a parent for all the Action executors classes (Command, Query or Recommendation). It has an abstract method execute that executes the action and returns a result String.

Actual action execution

Each action type is parsed and executed inside its own class. Each class implements the execute function with a switch based on the type of the command / query / recommendation, which calls the appropriate method.

I think the code is well commented and I will not explain each action function in this readme.

Important notes

• I used very often the Stream API, which helped me along with sorting, filtering and ordering my collections.
• For sorting, I used a Comparator with all the criterias chained with comparing().thenComparing().
• For Query, I implemented 3 internal classes, that handle each object type because many methods were implemented differently for each of them (e.g. filters).
• If I did not write a Javadoc for a method, it is because my method definitions are enough to understand what a method does. (eg. returnFistUnseen)
• The main tools that I used were filtering and sorting collections. With these, I accomplished almost every task.
• In my abstract Show model, I have some methods that are implemented differently for a Movie or a Serial (e.g. getShowRating or addRating) because the rating systems are different between these 2.