java-concurrency

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Java Concurrency Skill

Java并发编程技能

Master Java concurrency patterns for thread-safe applications.

掌握用于线程安全应用的Java并发编程模式。

Overview

概述

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

本技能涵盖从基础线程到Virtual Threads（Java 21+）的并发编程内容，包括线程池、同步机制以及CompletableFuture。

When to Use This Skill

何时使用本技能

Use when you need to:

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

当你需要以下操作时使用：

编写线程安全的代码
实现并行处理
使用异步编程模式
调优线程池
调试并发问题

Topics Covered

涵盖主题

Thread Management

线程管理

Thread lifecycle and states
Daemon vs user threads
Interrupt handling

线程生命周期与状态
守护线程 vs 用户线程
中断处理

Synchronization

同步机制

synchronized, volatile
Lock interfaces (ReentrantLock)
Atomic operations

synchronized、volatile
Lock接口（ReentrantLock）
原子操作

Executors

执行器

ThreadPoolExecutor configuration
ForkJoinPool
Virtual Threads (Java 21+)

ThreadPoolExecutor配置
ForkJoinPool
Virtual Threads（Java 21+）

CompletableFuture

Async execution
Chaining and composition
Exception handling

异步执行
链式调用与组合
异常处理

Quick Reference

快速参考

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();
    }
}

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

线程池大小设置

Workload	Formula	Example
CPU-bound	cores	8 threads
I/O-bound	cores * (1 + wait/compute)	80 threads

工作负载	计算公式	示例
CPU密集型	核心数	8个线程
I/O密集型	核心数 * (1 + 等待时间/计算时间)	80个线程

Troubleshooting

故障排查

Problem	Cause	Solution
Deadlock	Circular lock	Lock ordering, tryLock
Race condition	Missing sync	Add locks/atomics
Thread starvation	Unfair scheduling	Fair locks

问题	原因	解决方案
死锁	循环锁	锁排序、tryLock
竞态条件	缺少同步机制	添加锁/原子操作
线程饥饿	不公平调度	公平锁

Debug Commands

调试命令

bash

jstack -l <pid> > threaddump.txt
jcmd <pid> Thread.print

bash

jstack -l <pid> > threaddump.txt
jcmd <pid> Thread.print

Usage

使用方法

Skill("java-concurrency")

Skill("java-concurrency")