java-reviewer_skill

Overview

This skill reviews Java code for idiomatic patterns, exception handling, resource management, null-safety, collection/stream usage, and adoption of modern Java (17+) features. It targets plain Java projects (Maven/Gradle) and source under src/main/java. It does not cover Spring, Android, or Kotlin-specific code.

How this skill works

The reviewer scans project files and build metadata to detect Java version and build tool, then analyzes source for critical anti-patterns: empty or overly-broad catch blocks, mutable static state, raw types, improper resource handling, and unsafe null/collection usage. It reports severity-classified findings and suggests concrete fixes and modern Java alternatives (pattern matching, records, switch expressions, text blocks).

When to use it

• Requesting a Java code review or modernization audit
• Checking exception handling or resource management practices
• Validating null safety and collection return contracts
• Evaluating streams and collection processing for anti-patterns
• Adopting Java 17+ language features across a codebase

Best practices

• Fail fast: validate inputs and reject invalid state early
• Prefer immutability: use final fields, unmodifiable collections, or records
• Use try-with-resources for all closeable resources
• Avoid empty catch blocks and do not catch Throwable; handle specific exceptions
• Return empty collections instead of null and make defensive copies when exposing internal lists

Example use cases

• Scan a Maven or Gradle project to flag empty catch blocks and broad Exception catches
• Convert verbose DTOs to records and replace instanceof casts with pattern matching
• Detect mutable public static fields and suggest thread-safe alternatives
• Replace manual close() calls with try-with-resources and fix resource leaks
• Refactor stream usage: replace forEach-side-effects with collect, avoid unnecessary parallel streams