1. Classes can be of multiple types - yoga, gym, dance.
2. Each class has a capacity. This refers to the maximum number of users that can attend the class.
3. Users can book a class if the capacity is not yet reached.
4. If a class is already at capacity, the system should maintain a waiting list of interested users.
5. Users can cancel the slot upto 30 mins before the class starts. When a user cancels their booking, allocate the canceled slot to the first user from the waitlist.

The app contains two files :

• Book.java contains the bussiness logic of the app
• Classes.java contains the main class for storing classes and their attributes like currentUsers, currentSlots, etc.

The Classes.java contains methods to check if user can cancel a class, join a class, check if a class is full, update the queue, etc.

• To add a class, input the class details like Name, totalSlots, etc.

• To join a class, input your userName and the className you want to join.

• If the class is full, the user is added to a queue and the error message and queue is displayed.

• I haven't made an extra class for User as we were allowed to use just names for the app functioning.
• The code might feel less modular due to time constraint, otherwise I would have seperated the database operations from Book.java altogether.
• I have used a simple array for storing the queue of users, could have used Queue data structure.