Why this module matters
Most developers learn design patterns as theory. In real projects, the challenge is different: you must pick the right pattern quickly, explain trade-offs clearly, and deliver maintainable code. This module helps you do exactly that with simple examples, tests, and decision guides.
- Learn by reading concise Java implementations.
- Learn by running JUnit tests that show behavior.
- Use a practical decision flow for business problems.
Quick pattern-selection playbook
Use this simple shortlist when facing common business needs:
Then validate your choice with 3 checks: Fit (solves core need), Cost (acceptable complexity), and Evolvability (still useful as your domain grows).
What you will find inside
Classic pattern families: Creational, Structural, Behavioral, and SOLID principles.
Enterprise patterns: resilience, data consistency, architecture boundaries, and integration styles used in production systems.
Modern additions: cloud-native observability and AI application patterns (prompt building, retrieval orchestration, tool/agent facade, fallback strategy, safety wrappers, and evaluation harness).
Simple learning path (industry-first)
- Start with SOLID and Strategy.
- Then learn Factory Method, Abstract Factory, and Builder.
- Add Observer, Adapter, Decorator, and Facade.
- Move to Command, Chain of Responsibility, and State.
- Finally, go deeper with CQRS, Event Sourcing, and architecture patterns.
This order gives strong practical value for backend and platform engineering work.
How to run locally
mvn test
mvn verify
mvn -Dtest=SingletonTest test
Prerequisites: JDK 21+ and Maven 3.9+. If you are in a corporate environment, configure proxy or mirror settings in ~/.m2/settings.xml.
Final takeaway
Design patterns are not just interview topics. They are decision tools for shipping reliable software in real business systems. Use this module as your playbook whenever you need a fast, explainable, and scalable design choice.
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