Java Design Patterns Mini

A collection of essential design patterns implemented in Java.

Patterns Included

Singleton Pattern

• SimpleSingleton: Basic singleton with lazy initialization
• BillPughSingleton: Thread-safe singleton using static inner class (Initialization on demand holder)

Factory Pattern

• AppFactory: Creates different app types based on environment
• App: Abstract base class for applications
• Concrete Apps: AndroidApp, iOSApp, DesktopApp, WatchApp, FlutterApp

Running the Examples

Each pattern includes a main method for demonstration:

# Singleton examples
cd java/SingletonExample/src && javac com/company/SimpleSingleton.java && java com.company.SimpleSingleton
cd java/bill-pugh-singleton/src && javac com/company/BillPughSingleton.java && java com.company.BillPughSingleton

# Factory pattern example
cd java/factory-pattern/src && javac com/company/*.java && java com.company.GrzAppCatalog

Project Structure

java/
├── SingletonExample/          # Basic singleton implementation
├── bill-pugh-singleton/       # Thread-safe singleton
└── factory-pattern/           # Factory pattern with app creation