Java Vending Machine Project: OOP Concepts & Simulation
Explore a Java mini project simulating a Smart Vending Machine. Learn about OOP principles, state management, and transaction logic in Java.
Java Mini Project: Smart Vending Machine
Course: BCS306A - Object Oriented Programming with Java
Presented by: [Student Name] | USN: [Your USN] Semester: 3rd | Section: [A/B]
Smt. Kamala & Sri Venkappa M. Agadi College of Engineering and Technology, Lakshmeshwar Department of Information Science & Engineering
Guide: Mrs. Prathima Mahapurush (Course Coordinator)
Introduction
The Vending Machine System is a simulation of an automated machine that dispenses items such as snacks and beverages to users after money is inserted and a selection is made.<br><br><b>Purpose of the Project:</b><br>To demonstrate core Object-Oriented Programming (OOP) concepts in Java, including encapsulation, state management, and exception handling, by modeling a real-world self-service kiosk.
Problem Statement
Manual retail counters require constant human presence, leading to high labor costs.
Human handling of small cash transactions is prone to calculation errors.
Traditional shops have limited operating hours, whereas users need 24/7 access to basic supplies.
This project solves these issues by automating the inquiry, payment, and dispensing process.
Objectives
To design a class structure that accurately models Products, Inventory, and Currency.
To implement logical checks for stock availability and sufficient funds.
To demonstrate the 'State Pattern' or switch-logic for machine states (Idle, Select, Pay, Dispense).
To ensure robust error handling for user inputs (e.g., negative money, invalid codes).
Scope of the Project
<b>System Covers:</b><br>- Inventory maintenance (add/remove items).<br>- Transaction processing (calculating total price vs. inserted cash).<br>- Change calculation logic.<br>- User Interface (Console based simulation).<br><br><b>Limitations:</b><br>- No physical hardware integration.<br>- Does not handle credit card processing APIs (simulation only).
Technologies Used
Programming Language: Java (JDK 17 or higher)
IDE: Eclipse / IntelliJ IDEA / NetBeans
Concepts: OOP (Classes, Interfaces, Enums), Java Collections Framework (Map/List for Inventory)
Tools: Git for version control (optional)
System Architecture
The architecture follows a sequential control flow:<br>1. <b>Start:</b> System initializes inventory.<br>2. <b>Input:</b> User inputs money and selects code.<br>3. <b>Process:</b> Validation Logic runs (Is code valid? Is balance > price?).<br>4. <b>Action:</b> Dispense Product & Return Balance OR Display Error.<br>5. <b>Termination:</b> Transaction completes; return to idle.
Implementation (Core Logic)
public class VendingMachine { private Map<String, Integer> prices = new HashMap<>(); private int balance = 0; public VendingMachine() { prices.put("A1", 25); // Set price for item A1 } public void insertMoney(int amount) { balance += amount; System.out.println("Balance: " + balance); } public String selectItem(String code) { if (!prices.containsKey(code)) return "Invalid Selection"; int cost = prices.get(code); if (balance < cost) return "Insufficient Funds"; balance -= cost; return "Dispensing Item... Change: " + balance; } }
Output Screens
The console interface guides the user through the process.<br><Br><b>Step 1:</b> Menu Display.<br><b>Step 2:</b> Money Insertion Confirmation.<br><b>Step 3:</b> Successful Transaction message with change calculation.
Results & Analysis
The system was tested with various scenarios to ensure reliability.<br><br><b>Achievements:</b><br>- 100% calculation accuracy for change dispensing.<br>- Robust handling of 'Out of Stock' events.<br>- Reduced transaction time compared to manual processing.
Conclusion
The Java Mini Project successfully implements a Vending Machine simulation. It validates the use of Object Oriented Programming to solve real-world automation problems, providing a scalable foundation that could later be connected to a physical database or hardware interface.
References
Herbert Schildt, 'Java: The Complete Reference', 11th Edition.
Kathy Sierra & Bert Bates, 'Head First Java'.
Oracle Java Documentation (docs.oracle.com).
GeeksForGeeks - Java OOP Concepts.
Thank You
Questions?
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