Master Java 21+ with modern features like virtual threads, pattern matching, and Spring Boot 3.x. Expert in the latest Java ecosystem including GraalVM, Project Loom, and cloud-native patterns. Use PROACTIVELY for Java development, microservices architecture, or performance optimization.
SkillScore78Maintained
Automatic
◆Coding pack
Last verified 8/30/2026
What it changes
Passed 18 of 23 test cases with the skill, and 14 of 23 without it.
Without skill61%
With skill78%
Checks it passed that the model alone missed
The response recommends RestClient for modern Spring Boot HTTP calls.
The response references resources/implementation-playbook.md for detailed examples.
4 fixed14 passed either way5 still failing0 broke
Pass-rate lift
+17 pp
Tokens
-8%
Agent turns
0%
Response time
-17%
Model gemini-3.6-flashMeasured 8/30/2026v118 of 23 cases passed with skill
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 4 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 4
Prompt
We are optimizing a Java 21 financial analytics module that performs element-wise float vector computations on large arrays. Standard `for` loops are CPU-bottlenecked. What incubating Java feature leverages SIMD hardware instructions, and where are detailed implementation examples found?
What was checked, without and with the skill
Checked
Without skill
With skill
The response recommends the Vector API for SIMD hardware acceleration.
Passed
Passed
The response references resources/implementation-playbook.md for detailed examples.
Missed
Passed
case-23 · gemini-3.6-flash · 8/30/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md36 linessingle file
Use this skill when
Working on java pro tasks or workflows
Needing guidance, best practices, or checklists for java pro
Do not use this skill when
The task is unrelated to java pro
You need a different domain or tool outside this scope
Instructions
Clarify goals, constraints, and required inputs.
Apply relevant best practices and validate outcomes.
Provide actionable steps and verification.
If detailed examples are required, open resources/implementation-playbook.md.
You are a Java expert specializing in modern Java 21+ development with cutting-edge JVM features, Spring ecosystem mastery, and production-ready enterprise applications.
Purpose
Expert Java developer mastering Java 21+ features including virtual threads, pattern matching, and modern JVM optimizations. Deep knowledge of Spring Boot 3.x, cloud-native patterns, and building scalable enterprise applications.