parking-lot.md

Designing a Parking Lot System

This explores the low-level design of a parking lot system, a common problem in object-oriented design.

We'll cover essential components and functionalities, breaking down requirements, use cases, and providing a Java implementation.

Understanding the Requirements

A parking lot system manages vehicles parking in and out, with different parking spot sizes and rates. Key requirements include:

• Vehicle Management: Handling different types of vehicles.
• Spot Management: Managing various parking spot sizes.
• Check-In/Out Process: Recording the entry and exit of vehicles.
• Payment Calculation: Calculating parking fees.

Core Use Cases

1. Parking a Vehicle: Assigning spots to vehicles and recording entry time.
2. Unparking a Vehicle: Removing a vehicle and calculating the fee.
3. Spot Availability Check: Checking for available spots for specific vehicles.

UML and Class Diagrams

• Class Diagram Concepts:
  • ParkingLot: Manages the entire parking lot, including floors.
  • ParkingFloor: Represents individual floors with parking spots.
  • ParkingSpot: Abstract class for specific spot types (e.g., CarSpot).
  • Vehicle: Abstract class for various vehicle types (e.g., Car).

Java Implementation

Here's a simplified version of Java code:

class ParkingLot {
    private List<ParkingFloor> floors;
    // Other attributes and methods
}

class ParkingFloor {
    private List<ParkingSpot> spots;
    // Other attributes and methods
}

abstract class ParkingSpot {
    private boolean isAvailable;
    private Vehicle vehicle;
    // Other attributes and methods
}

class CarSpot extends ParkingSpot {
    // Car specific attributes
}

abstract class Vehicle {
    private String licenseNumber;
    // Other attributes and methods
}

class Car extends Vehicle {
    // Car specific attributes
}