pluginagentmarketplace/custom-plugin-java/java-concurrency

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Master Java concurrency - threads, executors, locks, CompletableFuture, virtual threads

Install

npx vskill@latest install pluginagentmarketplace/custom-plugin-java/java-concurrency

SKILL.md

Java Concurrency Skill

Master Java concurrency patterns for thread-safe applications.

Overview

This skill covers concurrency from basic threads to virtual threads (Java 21+), including thread pools, synchronization, and CompletableFuture.

When to Use This Skill

Use when you need to:

  • Write thread-safe code
  • Implement parallel processing
  • Use async programming patterns
  • Tune thread pools
  • Debug concurrency issues

Topics Covered

Thread Management
  • Thread lifecycle and states
  • Daemon vs user threads
  • Interrupt handling
Synchronization
  • synchronized, volatile
  • Lock interfaces (ReentrantLock)
  • Atomic operations
Executors
  • ThreadPoolExecutor configuration
  • ForkJoinPool
  • Virtual Threads (Java 21+)
CompletableFuture
  • Async execution
  • Chaining and composition
  • Exception handling

Quick Reference

java
// Virtual Threads (Java 21+)
try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
IntStream.range(0, 10_000).forEach(i ->
executor.submit(() -> processRequest(i)));
}
// CompletableFuture composition
CompletableFuture<Result> result = fetchUser(id)
.thenCompose(user -> fetchOrders(user.id()))
.thenApply(orders -> processOrders(orders))
.exceptionally(ex -> handleError(ex))
.orTimeout(5, TimeUnit.SECONDS);
// Thread pool configuration
ThreadPoolExecutor executor = new ThreadPoolExecutor(
10, 50, 60L, TimeUnit.SECONDS,
new ArrayBlockingQueue<>(1000),
new ThreadPoolExecutor.CallerRunsPolicy()
);
// Lock with timeout
ReentrantLock lock = new ReentrantLock();
if (lock.tryLock(1, TimeUnit.SECONDS)) {
try {
// critical section
} finally {
lock.unlock();
}
}

Thread Pool Sizing

WorkloadFormulaExample
CPU-boundcores8 threads
I/O-boundcores * (1 + wait/compute)80 threads

Troubleshooting

ProblemCauseSolution
DeadlockCircular lockLock ordering, tryLock
Race conditionMissing syncAdd locks/atomics
Thread starvationUnfair schedulingFair locks
Debug Commands
bash
jstack -l <pid> > threaddump.txt
jcmd <pid> Thread.print

Usage

Skill("java-concurrency")

Security

  • Security scanPassed, 100 of 100Pattern checks on the skill's files.
  • Model reviewNot runA model review is scheduled for the next rescan.

Quality evaluation

  • Task evaluationNot runNo evaluation yet. Run one in Skill Studio.

Source

Popularity

Repository stars
28
Repository forks
4
7-day trend score
17

Stars and forks are for the whole GitHub repository, not this skill alone. Refreshed 23 Mar 2026, 7 months ago.

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