It is a very basic parking lot implementation.

There can be many improvements:

1. ParkingSlot can be an interface/abstract class and bike, car, truck slot can implement/extend it.
2. Use ParkingStrategy in ParkingLot to make it more versatile.

• Singleton - to get a single instance of parking lot
• Strategy - to create a pricing strategy
• Factory - to get instances

• Parking spot types
• Parking spots
• Parking floors
• Parking ticket
• Parking lot
• Pricing strategy
• Parking entry/exit