In this lesson, we’ll identify and design the classes, abstract classes, and interfaces based on the requirements that we have previously gathered from the interviewer in our Facebook social network system.

Components of Facebook

As mentioned earlier, we will design the Facebook social network using a bottom-up approach.


The Account class identifies a Facebook user using their username and ID. Users with an account will have the option to create groups, pages, posts, comments, and like other comments and posts.

A representation of the class definition is provided below:

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