## 🧩 Java Development Rules 

### ✅ General Coding Standards
- Use meaningful and descriptive variable, method, and class names.
- Follow camelCase for variables and methods, PascalCase for classes.
- Avoid magic numbers and hardcoded values; use constants or enums.
- Keep methods short and focused on a single responsibility.
- Prefer composition over inheritance where applicable.
- Avoid deep nesting; use early returns to simplify logic.

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### 🧪 Testing Best Practices
- Always write unit tests for public methods using JUnit 5.
- Use Mockito for mocking dependencies in unit tests.
- Follow AAA (Arrange-Act-Assert) pattern in tests.
- Ensure tests are independent and repeatable.
- Use parameterized tests for multiple input scenarios.
- Validate edge cases and exception handling in tests.
- Use integration tests for Spring Boot controllers and services.

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### 🛡️ Defensive Programming
- Validate method inputs using `Objects.requireNonNull()` or custom checks.
- Use `Optional` to handle nullable return values safely.
- Catch and log exceptions with meaningful messages.
- Avoid exposing internal implementation via public APIs.
- Use assertions only for development, not production logic.
- Handle external API failures gracefully with retries or fallbacks.

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### 🚀 Optimization & Modern Java Features
- Use `var` for local variables where type is obvious (Java 10+).
- Prefer `switch` expressions over traditional switch (Java 14+).
- Use `record` for immutable data carriers (Java 14+).
- Use `Stream` API for collection processing, but avoid overuse.
- Use `CompletableFuture` for async operations.
- Use `Pattern Matching for instanceof` (Java 16+) for cleaner type checks.
- Use `Text Blocks` for multi-line strings (Java 15+).
- Avoid unnecessary object creation; reuse where possible.
- Profile and benchmark critical code paths before optimizing.

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### 🌱 Spring Boot Specific Rules
- Use constructor injection over field injection.
- Annotate configuration classes with `@Configuration`.
- Use `@Service`, `@Repository`, and `@Controller` appropriately.
- Avoid business logic in controllers; delegate to services.
- Use `@Transactional` for methods that modify data.
- Externalize configuration using `application.yml` or `application.properties`.
- Use `@Value` or `@ConfigurationProperties` for config binding.
- Validate request payloads using `@Valid` and `@NotNull`, etc.
- Use pagination and filtering for large data sets.
- Secure endpoints using Spring Security best practices.