Design Pattern Examples (Java)

This repository is a curated set of Java examples for common software design patterns.

Prerequisites

• Java 17+

Structure

src/main/java/
├── singleton/          # Creational
├── factorymethod/
├── abstractfactory/
├── prototype/
├── builder/
├── adapter/            # Structural
├── decorator/
├── composite/
├── facade/
├── proxy/
├── strategy/           # Behavioral
├── observer/
├── command/
├── templatemethod/
├── state/
└── chain/              # Chain of Responsibility

Each pattern package contains:

• Example.java: a runnable example with a main method.
• README.md: explains the problem, how the pattern works, key roles, and example flow.

Smoke tests live in src/test/java/.

Included patterns

Creational

• Singleton (singleton)
• Factory Method (factorymethod)
• Abstract Factory (abstractfactory)
• Prototype (prototype)
• Builder (builder)

Structural

• Adapter (adapter)
• Decorator (decorator)
• Composite (composite)
• Facade (facade)
• Proxy (proxy)

Behavioral

• Strategy (strategy)
• Observer (observer)
• Command (command)
• Template Method (templatemethod)
• State (state)
• Chain of Responsibility (chain)

Build

./gradlew build

Run one example

./gradlew runExample -Ppattern=strategy

Available values for -Ppattern: singleton, factorymethod, abstractfactory, prototype, builder, adapter, decorator, composite, facade, proxy, strategy, observer, command, templatemethod, state, chain.

Run all examples

./gradlew runAll

Run tests

./gradlew test