java-conventions

name	java-conventions
description	Java code conventions covering Java 17+ records and sealed classes, formatting/static analysis, Maven/Gradle, JUnit 5, exception handling, constructor injection, streams, and security. Load when writing or reviewing Java code.

• Java 17+ LTS, records for immutable data, sealed classes for restricted hierarchies, pattern matching.
• A consistent style guide and auto-formatter (e.g., Google Java Style + google-java-format). Static analysis (e.g., Error Prone + SpotBugs).
• Build: Maven or Gradle with wrapper scripts (mvnw/gradlew). Commit wrapper files.
• Testing: JUnit 5 with @ParameterizedTest, an assertion library (e.g., AssertJ), a coverage tool (e.g., JaCoCo) at 80%+.
• Benchmarking: JMH for microbenchmarks — never use System.nanoTime() loops.
• Error handling: specific exceptions only, never catch (Exception), use try-with-resources for AutoCloseable.
• var for obvious types, Optional<T> for returns (never params/fields), final fields by default.
• Prefer constructor injection over field injection for DI. Immutable collections: List.of(), Map.of().
• Streams for collection transforms, instanceof pattern matching, switch expressions.
• Security: OWASP dependency-check Maven/Gradle plugin for CVE scanning.
• Dependencies: commit lock files, use BOM for version alignment, avoid SNAPSHOT in releases.
• Anti-patterns: public fields, mutable static state, raw types, checked exceptions in lambdas.