Vending Machine

Question

Architect and write skeleton code for a modular vending machine. Vending machines should have a base which handles taking money, credit card, etc... and accepts pluggable racks which contain spindles which hold/dispense product. This question would be more to see how Candidates design the software, if they use SOLID principles, Design Patterns, etc...

High-Level Architecture

• Vending Machine: Handles payment processing (cash, credit card, etc.).
• Pluggable Racks: Each rack can be plugged into the base and contains spindles for dispensing products.
• Spindles: Hold and dispense products.

Key Components

• Payment System: Interface for different payment methods.
• Vending Machine Base: Manages the overall operation and integrates with racks.
• Rack: Pluggable component that holds spindles.
• Spindle: Mechanism to hold and dispense products.

Design Patterns Used

• Strategy Pattern: For different payment methods.
• State Pattern:For Managing different states of the Vending Machine
• Singleton(Thread Safe) : For maintaining Consistency and Integrity for Vending Machine

Explanation

• PaymentMethod: An interface for different payment methods.
• CashPayment and CardPayment: Concrete implementations of the PaymentMethod.
• Spindle: Represents a spindle that can dispense products.
• Rack: Contains multiple spindles and can dispense products from a specific spindle.
• VendingMachine : Manages the payment system and racks, and coordinates the dispensing of products.

Classes, Interfaces and Enumerations

• The Product class represents a product in the vending machine, with properties such as name and price.
• The Coin and Note enums represent the different denominations of coins and notes accepted for CashPayment.
• The Inventory class manages the available products and their quantities in the vending machine.
• The VendingMachineState interface defines the behavior of the vending machine in different states, such as idle, Select, and dispense.
• The IdleState,SelectState, and DispenseState classes implement the VendingMachineState interface and define the specific behaviors for each state.
• The VendingMachine class is the main class that represents the vending machine. It follows the Singleton pattern to ensure only one instance of the vending machine exists.
• The VendingMachine class maintains the current state, paymentMethod provides methods for state transitions and payment handling.