Business Game 🏦

A Monopoly-style business simulation game built in Java, featuring real-time stock price fluctuations, property trading across 26 world cities, and multi-player account management — all played through an interactive console.

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Table of Contents

• Features
• Project Structure
• Architecture Overview
• Getting Started
• How to Play
• Class Reference
• Known Bugs Fixed
• Future Improvements

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Features

Feature	Description
Multi-player accounts	Up to 100 player accounts with PIN authentication
Live stock market	Background thread fluctuates the share price ±$10 every 10 seconds
ASCII stock chart	Price history visualised in the terminal
Property trading	Buy/sell city properties across 26 world cities
Round inflation	Type 11 to end a round and apply 5 % price inflation to all properties
Fund transfers	Securely move money between accounts
Save to file	Persist account balances to accounts.txt

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Project Structure

BusinessGame/
├── pom.xml                                 ← Maven build file
├── README.md
└── src/
    └── main/
        └── java/
            └── com/businessgame/
                ├── Main.java               ← Entry point & dependency wiring
                │
                ├── model/                  ← Pure domain objects (no I/O)
                │   ├── Account.java        ← Player account: balance, shares, properties
                │   └── Property.java       ← City/country: name, price, index
                │
                ├── service/                ← Business logic layer
                │   ├── AccountRegistry.java    ← In-memory account store
                │   ├── PropertyMarket.java     ← Property catalogue & round inflation
                │   ├── StockMarket.java        ← Thread-safe share price + fluctuator
                │   ├── StockChart.java         ← ASCII chart renderer
                │   └── SaveService.java        ← Persist accounts to file
                │
                ├── ui/                     ← Console I/O handlers
                │   ├── GameMenu.java           ← Main game loop & top-level menu
                │   ├── AccountUI.java          ← Account commands (create, balance, …)
                │   ├── PropertyUI.java         ← Property sub-menu
                │   └── MarketUI.java           ← Stock market sub-menu
                │
                └── util/
                    └── InputHelper.java        ← Safe Scanner wrapper with retry logic

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Architecture Overview

┌─────────────────────────────────────────────┐
│                   Main.java                 │
│  Wires services → GameMenu → runs game loop │
└───────────────────┬─────────────────────────┘
                    │
        ┌───────────▼───────────┐
        │       GameMenu        │
        │  (top-level commands) │
        └──┬──────┬──────┬──────┘
           │      │      │
     AccountUI PropertyUI MarketUI
           │      │      │
           └──────┴──┬───┘
                     │  delegates to
          ┌──────────▼──────────┐
          │      Services       │
          │  AccountRegistry    │
          │  PropertyMarket     │
          │  StockMarket        │
          │  SaveService        │
          └──────────┬──────────┘
                     │  owns
          ┌──────────▼──────────┐
          │       Models        │
          │  Account            │
          │  Property           │
          └─────────────────────┘

All I/O is confined to the ui package. Services and models have zero System.out dependencies — they throw typed exceptions that the UI layer catches and presents as friendly messages.

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Getting Started

Prerequisites

• Java 17 or later
• Maven 3.8+ (or use the included wrapper if present)

Build

mvn clean package

This produces a runnable fat-jar at target/business-game-1.0.0.jar.

Run

java -jar target/business-game-1.0.0.jar

Or run directly from source:

mvn exec:java -Dexec.mainClass=com.businessgame.Main

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How to Play

On launch you will see the main menu. Type the number for the action you want and press Enter.

╔══════════════════════════════════════╗
║         BUSINESS GAME  v1.0          ║
╠══════════════════════════════════════╣
║   0  Check balance                   ║
║   1  Add balance                     ║
║   2  Withdraw funds                  ║
║   3  Property dealing                ║
║   4  Transfer funds                  ║
║   5  Stock market                    ║
║   7  Save game to file               ║
║   9  New account                     ║
║  11  End of round                    ║
║  99  Quit                            ║
╚══════════════════════════════════════╝

Typical game flow

1. Create accounts — each player types 9 to register with a unique account number and PIN.
2. Add starting money — the banker types 1 and deposits the agreed starting amount (a 10 % bonus is added automatically).
3. Take turns — players buy/sell properties (3) and trade on the stock market (5).
4. End each round — type 11 to advance the round; all property prices rise by 5 %.
5. Save progress — type 7 to write balances to accounts.txt.
6. Quit — type 99 when the game ends.

Available cities / countries

Code	City	Start Price
new	New York	$8,500
rom	Rome	$3,000
hon	Hong Kong	$2,500
syd	Sydney	$4,500
dub	Dubai	$5,000
kua	Kuala Lumpur	$3,500
deh	Delhi	$4,500
ber	Berlin	$5,000
rai	Riyadh	$9,500
zur	Zurich	$5,500
tok	Tokyo	$3,500
lon	London	$4,500
air	(top city)	$10,500
mos	Moscow	$5,000
…	…	…

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Class Reference

model/Account

Encapsulates all per-player state: balance, share count, property holdings, and PIN. Throws IllegalArgumentException / IllegalStateException on invalid operations — callers never check raw array bounds.

model/Property

Immutable city descriptor with a mutable price. applyRoundInflation() applies the 5 % round increase.

service/AccountRegistry

HashMap-backed store replacing the original parallel arrays. Provides find(accountNumber) and authenticate(accountNumber, password) returning Optional<Account>.

service/PropertyMarket

Holds the catalogue of 26 Property objects. findByName() is case-insensitive. applyRoundInflation() delegates to each property.

service/StockMarket

Maintains an AtomicInteger share price, safe for concurrent access. Starts a daemon thread that fluctuates the price ±$10 every 10 seconds and prints an updated chart.

service/StockChart

Static utility — renders an ASCII bar chart of a price-history array. Separated from StockMarket so it can be tested independently.

service/SaveService

Writes all account balances to accounts.txt using a BufferedWriter inside a proper try-with-resources block.

ui/GameMenu

Main loop. Maps integer commands to handler calls. All sub-menus loop internally and return control here when the user exits.

ui/AccountUI, ui/PropertyUI, ui/MarketUI

Thin console-interaction layers. Each reads input via InputHelper, calls service/model methods, and prints results or exception messages.

util/InputHelper

Wraps Scanner. readInt(), readLong(), and readWord() retry indefinitely on bad input instead of crashing with InputMismatchException.

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Known Bugs Fixed

#	Original issue	Fix
1	Data race on static int stockprice mutated from two threads	Replaced with AtomicInteger in StockMarket
2	InputMismatchException crash on non-integer input	InputHelper retries with a clear error message
3	Fernflower decompiler garbage (var0, var10000, nested Throwable catch) in saveToFile	Rewritten with proper try-with-resources
4	static int o counter in main() breaks if account creation fails (counter still incremented)	AccountRegistry uses a HashMap; no index needed
5	checkPrice() had a pointless try/catch(Exception) around System.out.println	Removed
6	propertyDealing() used while(as == 0) flag instead of a boolean	Replaced with clean boolean active loop
7	No validation — negative amounts, zero-division, array out-of-bounds all possible	Every model method validates input and throws typed exceptions
8	Stock price could go to 0 or negative with repeated bad ticks	Math.max(MIN_PRICE, ...) guard in fluctuator
9	createAccount used a separate o index that was never bounds-checked	Registry enforces MAX_ACCOUNTS with a clear error
10	No way to exit the game cleanly	Added command 99 and a JVM shutdown hook

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Future Improvements

• Persistence — load accounts.txt on startup to resume a saved game
• Password hashing — use BCrypt instead of storing plain-text PINs
• GUI — Swing or JavaFX board view
• Network play — expose services over sockets or REST for remote players
• Unit tests — JUnit 5 tests for model layer (no I/O required)
• Event system — Chance/Community Chest cards that trigger random events