Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add nimadorostkar/Claude-Skills-collection --skill java-kotlingit clone --depth 1 https://github.com/nimadorostkar/Claude-Skills-collectionWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/nimadorostkar/claude-skills-collection/java-kotlin)<a href="https://agentmods.dev/skills/nimadorostkar/claude-skills-collection/java-kotlin"><img src="https://agentmods.dev/badge/skills/nimadorostkar/claude-skills-collection/java-kotlin/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/nimadorostkar/claude-skills-collection/java-kotlin"><img src="https://agentmods.dev/badge/skills/nimadorostkar/claude-skills-collection/java-kotlin.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00040 | $0.00885 |
| Opus 5 | $0.00020 | $0.00443 |
| Sonnet 5 | $0.00008 | $0.00177 |
| Haiku 4.5 | $0.00004 | $0.00089 |
Grade A, and why
java-kotlin scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 95 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Java and Kotlin
Purpose
Write JVM code that uses the modern language surface — records, sealed types, pattern matching, coroutines — instead of the 2010-era idioms most JVM codebases are still carrying.
When to Use
- Writing or reviewing Java 17+ or Kotlin.
- Migrating a codebase off Java 8 idioms.
- Designing domain models with records and sealed interfaces.
- Introducing coroutines to replace callback or thread-pool code.
- Diagnosing JVM memory, GC, or startup problems.
Capabilities
- Java: records, sealed interfaces, pattern matching for
switch, virtual threads,Optionaldiscipline. - Kotlin: coroutines, structured concurrency, flows, null safety, delegation, DSL builders.
- Java/Kotlin interop, including platform-type null hazards.
- Build configuration for Gradle (Kotlin DSL) and Maven.
- JVM tuning: heap sizing, GC selection, JFR profiling.
Inputs
- Source module, build file, and target JVM version.
- Whether the code is a library (binary compatibility matters) or an application.
Outputs
- Modern, immutable-by-default domain types.
- Concurrency that is structured and cancellable.
- Build configuration pinned to a specific toolchain.
Workflow
- Model — Domain values as records (Java) or data classes (Kotlin). Variants as sealed interfaces.
- Match exhaustively — Use pattern-matching
switch/whenso a new variant becomes a compile error. - Structure concurrency — Virtual threads (Java 21+) or coroutine scopes tied to a lifecycle.
- Guard nulls at the interop line — Every value crossing from Java into Kotlin is a platform type; annotate or validate it.
- Gate — Compile with warnings as errors; run SpotBugs/detekt and the test suite.
Best Practices
- Never return
nullfrom a public API. ReturnOptional, an empty collection, or a sealed "absent" variant. - Records are for data, not for behavior with hidden state. Keep them free of mutable references.
- In Kotlin,
!!is a defect marker. If you cannot remove it, the type is lying. - Never launch a coroutine in
GlobalScope. It has no cancellation owner. - Prefer
runCatchingonly in application boundaries; libraries throw typed exceptions. - Pin the toolchain in the build file so the JVM version is not an environment variable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 9d ago First seen · 95 lines · 40 tokens per session scan A 3edd60d94d13
java-kotlin is a skill published in the GitHub repository nimadorostkar/Claude-Skills-collection (26 stars, last pushed 25d ago), licensed MIT. It adds 40 tokens to every session and 885 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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