问题描述
我对CompletableFuture方法有疑问：
I have a question about CompletableFuture method:
public <U> CompletableFuture<U> thenApply(Function<? super T, ? extends U> fn)
事情是JavaDoc说的只是这个：
The thing is the JavaDoc says just this:
线程怎么样？这将在哪个线程中执行？如果未来由线程池完成怎么办？
What about threading? In which thread this is going to be executed? What if the future is completed by a thread pool?
推荐答案
docs可以帮助您更好地理解：
The policies as specified in the CompletableFuture docs could help you understand better:
使用 ForkJoinPool.commonPool（）执行没有显式Executor参数的所有异步方法
（除非它不支持一个
并行度至少为2，在这种情况下，新的Thread是为运行每个任务创建的
。为了简化监视，调试和
跟踪，所有生成的异步任务都是标记
接口的实例 CompletableFuture.AsynchronousCompletionTask 。
All async methods without an explicit Executor argument are performed using the ForkJoinPool.commonPool() (unless it does not support a parallelism level of at least two, in which case, a new Thread is created to run each task). To simplify monitoring, debugging, and tracking, all generated asynchronous tasks are instances of the marker interface CompletableFuture.AsynchronousCompletionTask.
更新 ：我也会建议阅读@Mike的，作为对文档细节的进一步有趣分析。
Update: I would also advice on reading this answer by @Mike as an interesting analysis further into the details of the documentation.
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