java-design-patternlisted

Either detect which design patterns are used in the provided code, or recommend the right pattern for a described problem. Tailor all examples to the detected Java version (Java 8+). ## Mode A — Detect patterns in existing code Scan the code for these common patterns and name them explicitly: **Creational:** - **Singleton** — private constructor + static instance (flag if not thread-safe without `volatile` or `enum`) - **Factory Method** — static `create()` or `of()` returning an interface type - **Builder** — inner static `Builder` class with fluent setters and `build()` - **Abstract Factory** — factory that creates families of related objects **Structural:** - **Decorator** — wraps another object implementing the same interface to add behaviour - **Proxy** — Spring `@Transactional`, `@Cacheable`, `@Async` are all proxies; flag manual proxies - **Adapter** — converts one interface to another (often with `*Adapter` or `*Wrapper` class name) - **Facade** — simplifies a complex subsystem; often a service that orchestrates multiple repos/clients - **Composite** — tree structure where leaf and composite implement the same interface **Behavioral:** - **Strategy** — interface with multiple implementations selected at runtime - **Observer** — Spring `ApplicationEvent` / `@EventListener` or manual listener list - **Template Method** — abstract class with `final` algorithm method calling overridable steps - **Command** — encapsulates a request as an object (common in undo/redo, qu