JCStress（Java Concurrency Stress Tests）是一个用于测试和验证Java并发程序正确性的工具。它是OpenJDK项目的一部分，旨在帮助开发人员发现并发程序中的竞态条件、死锁、内存可见性等问题。
JCStress提供了一组注解和API，使得编写并发测试变得简单和方便。使用JCStress，您可以定义和运行各种类型的并发测试，包括多线程竞争测试、内存可见性测试、有序性测试等。JCStress会自动执行大量的并发测试用例，并生成详细的测试报告，以帮助您分析和理解并发程序的行为。
JCStress的主要特点包括：
使用JCStress编写和运行并发测试的一般步骤包括：
测试用例1：
/* This is our first concurrency test. It is deliberately simplistic to show testing approaches, introduce JCStress APIs, etc. Suppose we want to see if the field increment is atomic. We can make test with two actors, both actors incrementing the field and recording what value they observed into the result object. As JCStress runs, it will invoke these methods on the objects holding the field once per each actor and instance, and record what results are coming from there. Done enough times, we will get the history of observed results, and that would tell us something about the concurrent behavior. How to run this test: $ java -jar jcstress-samples/target/jcstress.jar -t API_01_Simple ... .......... [OK] org.openjdk.jcstress.samples.api.API_01_Simple Scheduling class: actor1: package group 0, core group 0 actor2: package group 0, core group 0 CPU allocation: actor1: CPU #3, package #0, core #3 actor2: CPU #35, package #0, core #3 Compilation: split actor1: C2 actor2: C2 JVM args: [] RESULT SAMPLES FREQ EXPECT DESCRIPTION 1, 1 46,946,789 10.1% Interesting Both actors came up with the same value: atomicity failure. 1, 2 110,240,149 23.8% Acceptable actor1 incremented, then actor2. 2, 1 306,529,420 66.1% Acceptable actor2 incremented, then actor1. */// Mark the class as JCStress test.@JCStressTest// These are the test outcomes.@Outcome(id = "1, 1", expect = ACCEPTABLE_INTERESTING, desc = "Both actors came up with the same value: atomicity failure.")@Outcome(id = "1, 2", expect = ACCEPTABLE, desc = "actor1 incremented, then actor2.")@Outcome(id = "2, 1", expect = ACCEPTABLE, desc = "actor2 incremented, then actor1.")// This is a state object@Statepublic class API_01_Simple { int v; @Actor public void actor1(II_Result r) { r.r1 = ++v; // record result from actor1 to field r1 } @Actor public void actor2(II_Result r) { r.r2 = ++v; // record result from actor2 to field r2 }}测试用例2：
@JCStressTest@Outcome(id = {"1, 2", "2, 1"}, expect = ACCEPTABLE, desc = "Mutex works")@Outcome(id = "1, 1", expect = FORBIDDEN, desc = "Mutex failure")@Statepublic class Mutex_06_Semaphore { /* How to run this test: $ java -jar jcstress-samples/target/jcstress.jar -t Mutex_06_Semaphore */ /* ---------------------------------------------------------------------------------------------------------- Single-permit Semaphore can be used as a crude mutex too. Of course, this primitive is much more flexible, it can admit a few threads at once with more permits. On x86_64, AArch64, PPC64: RESULT SAMPLES FREQ EXPECT DESCRIPTION 1, 1 0 0.00% Forbidden Mutex failure 1, 2 254,394,919 50.23% Acceptable Mutex works 2, 1 252,081,625 49.77% Acceptable Mutex works */ private final Semaphore semaphore = new Semaphore(1); private int v; @Actor public void actor1(II_Result r) { try { semaphore.acquire(); // critical section r.r1 = ++v; semaphore.release(); } catch (InterruptedException e) { throw new IllegalStateException(e); } } @Actor public void actor2(II_Result r) { try { semaphore.acquire(); // critical section r.r2 = ++v; semaphore.release(); } catch (InterruptedException e) { throw new IllegalStateException(e); } }}JCStress是一个强大的工具，可以帮助开发人员测试和验证Java并发程序的正确性。它广泛应用于Java开发社区，并被认为是Java并发测试领域的事实标准。使用JCStress可以提高并发程序的质量和可靠性，减少并发问题的出现。
参考资料：
【1】https://github.com/openjdk/jcstress/tree/master/jcstress-samples/src/main/java/org/openjdk/jcstress/samples。
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