
125-java-concurrency
Use when you need to apply Java concurrency best practices — including thread safety fundamentals, ExecutorService thread pool management, concurrent design patterns like Producer-Consumer, asynchronous programming with CompletableFuture, immutability and safe publication, deadlock avoidance, virtual threads, structured concurrency, scoped values, backpressure, cancellation discipline, and observability for concurrent systems. This should trigger for requests such as Review Java code for concurrency; Review Java code for thread safety; Fix race conditions in Java concurrency code; Choose ExecutorService or virtual threads in Java; Improve synchronization and shared mutable state handling; Apply structured concurrency for related Java subtasks. Part of Plinth Toolkit
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/jabrena/plinth --skill 125-java-concurrency- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads 125-java-concurrency automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Java rules for Concurrency objects
Identify and apply Java concurrency best practices to improve thread safety, scalability, and maintainability by using modern java.util.concurrent utilities and virtual threads.
What is covered in this Skill?
- Thread safety fundamentals:
ConcurrentHashMap,AtomicInteger,ReentrantLock,ReadWriteLock, Java Memory Model ExecutorServicethread pool configuration: sizing, keep-alive, bounded queues, rejection policies, graceful shutdown- Producer-Consumer and Publish-Subscribe patterns with
BlockingQueue CompletableFuturefor non-blocking async composition (thenApply/thenCompose/exceptionally/orTimeout)- Immutability and safe publication (
volatile, static initializers) - Lock contention and false-sharing performance optimization
- Virtual threads (
Executors.newVirtualThreadPerTaskExecutor()) for I/O-bound scalability - Structured Concurrency (
StructuredTaskScope) for related subtasks in Java 27 preview ScopedValueoverThreadLocalfor immutable cross-task data- Cooperative cancellation and
InterruptedExceptiondiscipline - Backpressure with bounded queues and
CallerRunsPolicy - Deadlock avoidance via global lock ordering and
tryLockwith timeouts - ForkJoin/parallel-stream discipline for CPU-bound work
- Virtual-thread pinning detection (JFR
VirtualThreadPinned) - Thread naming and
UncaughtExceptionHandlerobservability - Fit-for-purpose primitives:
LongAdder,CopyOnWriteArrayList,StampedLock,Semaphore,CountDownLatch,Phaser
Scope: The reference is organized by examples (good/bad code patterns) for each core area. Apply recommendations based on applicable examples.
Constraints
Before applying any concurrency changes, ensure the project compiles. If compilation fails, stop immediately — compilation failure is a blocking condition. After applying improvements, run full verification.
- MANDATORY: Run
./mvnw compileormvn compilebefore applying any change - SAFETY: If compilation fails, stop immediately — compilation failure is a blocking condition that prevents any further processing
- VERIFY: Run
./mvnw clean verifyormvn clean verifyafter applying improvements - BEFORE APPLYING: Read the reference for detailed good/bad examples, constraints, and safeguards for each concurrency pattern
When to use this skill
- Review Java code for concurrency
- Review Java code for thread safety
- Fix race conditions in Java concurrency code
- Choose ExecutorService or virtual threads in Java
- Improve synchronization and shared mutable state handling
- Apply structured concurrency for related Java subtasks
Workflow
- Compile project before concurrency changes
Run ./mvnw compile or mvn compile and stop immediately if compilation fails.
- Read concurrency reference and analyze hotspots
Read references/125-java-concurrency.md and identify thread-safety, coordination, and throughput issues to address.
- Apply concurrency improvements
Implement suitable concurrency patterns, structured task scopes where they fit related subtasks, cancellation discipline, and fit-for-purpose primitives.
- Verify with full build
Run ./mvnw clean verify or mvn clean verify after applying improvements.
Reference
For detailed guidance, examples, and constraints, see references/125-java-concurrency.md.
FAQ
What does the 125-java-concurrency skill do?
Use when you need to apply Java concurrency best practices — including thread safety fundamentals, ExecutorService thread pool management, concurrent design patterns like Producer-Consumer, asynchronous programming with CompletableFuture, immutability and safe publication, deadlock avoidance, virtual threads, structured concurrency, scoped values, backpressure, cancellation discipline, and observability for concurrent systems. This should trigger for requests such as Review Java code for concurrency; Review Java code for thread safety; Fix race conditions in Java concurrency code; Choose ExecutorService or virtual threads in Java; Improve synchronization and shared mutable state handling; Apply structured concurrency for related Java subtasks. Part of Plinth Toolkit
How do I install 125-java-concurrency?
Run npx skills add https://github.com/jabrena/plinth --skill 125-java-concurrency in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/125-java-concurrency/ (personal) or .claude/skills/125-java-concurrency/ (project).
Which AI agents can use 125-java-concurrency?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is 125-java-concurrency safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains 125-java-concurrency?
It is published by jabrena in jabrena/plinth. It has 405 recorded installs.
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