125-java-concurrency

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Original

English

🇨🇳

Translation

Chinese

Java rules for Concurrency objects

Java并发对象规则

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

```
ExecutorService
```
thread pool configuration: sizing, keep-alive, bounded queues, rejection policies, graceful shutdown
Producer-Consumer and Publish-Subscribe patterns with
```
BlockingQueue
```

CompletableFuture

for 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
```
ScopedValue
```
over
```
ThreadLocal
```
for immutable cross-task data
Cooperative cancellation and
```
InterruptedException
```
discipline
Backpressure with bounded queues and
```
CallerRunsPolicy
```
Deadlock avoidance via global lock ordering and
```
tryLock
```
with timeouts
ForkJoin/parallel-stream discipline for CPU-bound work
Virtual-thread pinning detection (JFR
```
VirtualThreadPinned
```
)
Thread naming and
```
UncaughtExceptionHandler
```
observability

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.

通过使用现代

java.util.concurrent

工具类和虚拟线程，识别并应用Java并发最佳实践，以提升线程安全性、可扩展性和可维护性。

本技能涵盖哪些内容？

线程安全基础：

ConcurrentHashMap

、

AtomicInteger

、

ReentrantLock

、

ReadWriteLock

、Java内存模型

```
ExecutorService
```
线程池配置：大小设置、存活时间、有界队列、拒绝策略、优雅关闭
基于
```
BlockingQueue
```
的生产者-消费者与发布-订阅模式

用于非阻塞异步组合的

CompletableFuture

（

thenApply

thenCompose

exceptionally

orTimeout

）

不可变性与安全发布（
```
volatile
```
、静态初始化器）
锁竞争与伪共享性能优化
用于I/O密集型场景可扩展性的虚拟线程（
```
Executors.newVirtualThreadPerTaskExecutor()
```
）
替代
```
ThreadLocal
```
的
```
ScopedValue
```
用于不可变跨任务数据传递
协作式取消与
```
InterruptedException
```
规范
基于有界队列和
```
CallerRunsPolicy
```
的背压机制
通过全局锁排序和带超时的
```
tryLock
```
避免死锁
适用于CPU密集型任务的ForkJoin/并行流规范
虚拟线程固定检测（JFR
```
VirtualThreadPinned
```
）
线程命名与
```
UncaughtExceptionHandler
```
可观测性

适用场景匹配的原语：

LongAdder

、

CopyOnWriteArrayList

、

StampedLock

、

Semaphore

、

CountDownLatch

、

Phaser

范围：参考文档按每个核心领域的示例（良好/不良代码模式）组织。根据适用示例应用建议。

Constraints

约束条件

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 compile
```
or
```
mvn compile
```
before applying any change
SAFETY: If compilation fails, stop immediately — compilation failure is a blocking condition that prevents any further processing
VERIFY: Run
```
./mvnw clean verify
```
or
```
mvn clean verify
```
after applying improvements
BEFORE APPLYING: Read the reference for detailed good/bad examples, constraints, and safeguards for each concurrency pattern

在应用任何并发修改之前，确保项目能够编译。如果编译失败，请立即停止——编译失败是阻塞条件。应用改进后，运行完整验证。

强制要求：在应用任何修改前运行
```
./mvnw compile
```
或
```
mvn compile
```
安全规则：如果编译失败，请立即停止——编译失败是阻塞条件，阻止任何后续处理
验证步骤：应用改进后运行
```
./mvnw clean verify
```
或
```
mvn clean verify
```
应用前须知：阅读参考文档，了解每个并发模式的详细良好/不良示例、约束条件和防护措施

When to use this skill

何时使用本技能

Review Java code for concurrency

审查Java代码的并发问题

Workflow

工作流程

Compile project before concurrency changes

Run

./mvnw compile

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, cancellation discipline, and fit-for-purpose primitives.

Verify with full build

Run

./mvnw clean verify

mvn clean verify

after applying improvements.

在并发修改前编译项目

运行

./mvnw compile

或

mvn compile

，如果编译失败则立即停止。

阅读并发参考文档并分析热点问题

阅读

references/125-java-concurrency.md

，识别需要解决的线程安全、协调和吞吐量问题。

应用并发改进方案

实现合适的并发模式、取消规范以及适用场景匹配的原语。

通过完整构建验证

应用改进后运行

./mvnw clean verify

或

mvn clean verify

。

Reference

参考文档

For detailed guidance, examples, and constraints, see references/125-java-concurrency.md.

如需详细指导、示例和约束条件，请查看references/125-java-concurrency.md。