Build a class diagram for this problem? [2 points]

Implement your work in java? [8 points]

We need to develop an application to manage multiple social media platforms. When the user writes a message on any platform, this message will be posted automatically on three platforms (Facebook, Twitter, Instagram) using a visitor design pattern. In each social platform (if the message is written on the same platform, no new post needs to apply). Each social platform has a follower list, and the recent posts are automatically pushed to each follower in the list using an observer design pattern.