https://DevOpsCloud.io -- Cloud Monk Losang Jinpa, Ph.D., MCSE/MCT, GitOps DevOps Engineer

Java CountDownLatch.countDown() is a method in the Java CountDownLatch class that decrements the latch's count by one. When the count reaches zero, all waiting threads are released. Introduced in Java 2004 with Java 5, countDown() is used in concurrent programming to synchronize threads, such as in scenarios where multiple threads must finish their tasks before proceeding.

https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CountDownLatch.html