Agent-skills-standard java-concurrency

Implement modern concurrency with Virtual Threads and Structured Concurrency in Java. Use when implementing Java Virtual Threads (Java 21), Structured Concurrency with StructuredTaskScope, CompletableFuture pipelines, or debugging race conditions. (triggers: **/*.java, Thread, Executor, synchronized, lock, CompletableFuture, StructuredTaskScope, VirtualThread, AtomicInteger, async, race condition)

install

source · Clone the upstream repo

git clone https://github.com/HoangNguyen0403/agent-skills-standard

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/HoangNguyen0403/agent-skills-standard "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/java/java-concurrency" ~/.claude/skills/hoangnguyen0403-agent-skills-standard-java-concurrency && rm -rf "$T"

manifest: skills/java/java-concurrency/SKILL.md

source content

Java Concurrency

Priority: P1 (HIGH)

Implementation Guidelines

Virtual Threads (Java 21): Use for high-throughput I/O.
```
Executors.newVirtualThreadPerTaskExecutor()
```
.
Structured Concurrency: Use
```
StructuredTaskScope
```
to treat related tasks as single unit (Scope, Fork, Join).
Immutability: Share immutable data between threads to avoid race conditions.
CompletableFuture: Use for composing async pipelines (if not using Virtual Threads).
Atomic Variables: Use
```
AtomicInteger
```
,
```
LongAdder
```
for simple counters.
Locks: Prefer
```
ReentrantLock
```
/
```
ReadWriteLock
```
over
```
synchronized
```
for fine-grained control.
Thread Safety: Document
```
@ThreadSafe
```
or
```
@NotThreadSafe
```
.

Anti-Patterns

No new Thread(): Use Executors or virtual threads; never create threads manually.
No Pooling Virtual Threads: Virtual threads cheap; never pool them.
No Blocking in synchronized: Pins carrier thread (Loom pitfall); use ReentrantLock instead.
No Shared Mutable State: Share only immutable data between threads.
No Thread.stop/suspend: Deprecated; use interruption or cancellation instead.

References

StructuredTaskScope & VirtualThread Examples