performance-smell-detectionlisted

# Performance Smell Detection Skill Identify **potential** code-level performance issues in Java code. ## Philosophy > "Premature optimization is the root of all evil" - Donald Knuth This skill helps you **notice** potential performance smells, not blindly "fix" them. Modern JVMs (Java 21/25) are highly optimized. Always: 1. **Measure first** - Use JMH, profilers, or production metrics 2. **Focus on hot paths** - 90% of time spent in 10% of code 3. **Consider readability** - Clear code often matters more than micro-optimizations ## When to Use - Reviewing performance-critical code paths - Investigating measured performance issues - Learning about Java performance patterns - Code review with performance awareness ## Scope **This skill:** Code-level performance (streams, collections, objects) **For database:** Use `jpa-patterns` skill (N+1, lazy loading, pagination) **For architecture:** Use `architecture-review` skill --- ## Quick Reference: Potential Smells | Smell | Severity | Context | |-------|----------|---------| | Regex compile in loop | 🔴 High | Always worth fixing | | String concat in loop | 🟡 Medium | Still valid in Java 21/25 | | Stream in tight loop | 🟡 Medium | Depends on collection size | | Boxing in hot path | 🟡 Medium | Measure first | | Unbounded collection | 🔴 High | Memory risk | | Missing collection capacity | 🟢 Low | Minor, measure if critical | --- ## String Operations (Java 9+ / 21 / 25) ### What Changed Since **Java 9** (JEP 280), s