System Design Full Course - State Design Pattern | Build Vending Machine (UML & Code) | System Design

Welcome to Lecture 32 of the Ultimate Low-Level Design (LLD) Series by Coder Army! Seventh week for #lowleveldesign #systemdesign #8weeksLLdchallenge We are doing 8 weeks challenge and going to complete the whole course within the duration with quality content on Youtube. Let’s learn LLD like never before and attain advance level mastery on this subject. In this deep-dive Low-Level Design (LLD) tutorial, we explore the State Design Pattern using a classic vending machine example. You’ll learn how to: 1. Define the Context & State Interface – See how our `VendingMachine` holds a reference to a `VendingState` and delegates behavior. 2. Implement Concrete States – Walk through `NoCoinState`, `HasCoinState`, `DispenseState`, and `SoldOutState`, each encapsulating its own logic. 3. Handle Transitions Cleanly – Discover return-based transitions that keep states stateless and behavior-focused. 4. Simulate Real-World Flows – Watch a live demo: inserting coins, selecting items, dispensing, returning change, and handling sold-out scenarios. 5. Benefits & Best Practices – Understand why State Pattern simplifies complex conditional code, adheres to the Open/Closed Principle, and makes your code easier to extend and maintain. Whether you’re a seasoned developer or just starting your design-patterns journey, this tutorial will give you the clarity and confidence to apply the State Pattern in your own projects! Join Coder Army Whatsapp Group: https://www.youtube.com/redirect?event=video_description&redir_token=QUFFLUhqa09Qd2hqVW51V05sTlplN05fWGdNRi00VEhtd3xBQ3Jtc0trTU5rM3V0S3ZBWWRKOTExQWZHdUNqSFZSZHhNN1lnTThpN1c2VnQxR2g0OC0xT29rZ05UWVlFRzFuZmhhMEJwcmczRXB3U0RPNlFCZEdMQ2VDNmlJNVRUejJYQWhEeGsxUkJ4MzJNLVBXZzdPcXg3cw&q=https%3A%2F%2Fwhatsapp.com%2Fchannel%2F0029Va6H0tbHVvTbcuT99Y1f&v=Z9rFlZClYNI Code and Notes: Github : https://github.com/adityatandon15/LLD Connect with Aditya Tandon Instagram : https://www.instagram.com/adityatandon2 LinkedIn : https://www.linkedin.com/in/adityatandon2 Twitter : https://x.com/adityatandon02 00:00 Introduction 00:41 What is State Design Pattern 19:50 Complete State Machine Diagram 26:17 UML Diagram 43:38 Clean UML Diagram 45:18 Code for Vending Machine 01:08:27 Standard UML Diagram 01:09:46 Standard Definition 01:12:11 Real World Use cases #StatePattern #DesignPatterns #LowLevelDesign #LLD #VendingMachine #SoftwareDesign #OOP #CPlusPlus #Java #ProgrammingTutorial #CodeDesign #BehavioralPatterns #CleanCode #SOLID #DataStructures