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This article introduces the relevant knowledge of "how to use CountDownLatch in Java". Many people will encounter such a dilemma in the operation of actual cases, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

When developing multithreaded programs, there is often a requirement that the main thread can wait for the child thread to finish executing the logic of the main thread. According to what we have learned, we can use the join () method to achieve this requirement.

Let's call the join () method to meet our needs.

I won't explain too much about the use of the join () method here. If you want to know more, you can take a look at this article.

Let's use CountDownLatch to meet our needs.

CountDownLatch: allows one or more threads to wait for other threads to complete the operation. The constructor of the CountDownLatch must receive a parameter of type int. This parameter is the number of threads to wait for. If we have to wait for 2 threads, then we will write 2 as the parameter. When we call the countDown () method in CountDownLatch, the parameter is automatically subtracted by 1, and when the parameter becomes 0, the current thread is not blocked.

If the parameters in the CountDownLatch constructor are greater than the number of calls to the countDown () method in CountDownLatch, that is, the parameters will never be equal to 0. Then the current thread will be waiting. In actual multithreaded development, CountDownLatch is often used to meet our above needs, because compared with join (), it can be processed directly inside the thread without the need to call join () in the current thread.

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