CountDownLatch java 17

CountDownLatch java 17

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CountDownLatch is a Java class that allows one or more threads to wait at a single point until a set of operations being performed in another thread or threads complete. It's a useful synchronization tool when you have multiple threads waiting for a common resource, like a database connection or a file lock, to become available.

Here's an example of how to use CountDownLatch:

import java.util.concurrent.CountDownLatch;
public class MyRunnable implements Runnable {
private final CountDownLatch latch = new CountDownLatch(3); // Set the count to 3
public void run() {
try {
Thread.sleep(2000);
System.out.println("Thread " + Thread.currentThread().getName() + " has finished.");
latch.countDown();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
public static void main(String[] args) throws InterruptedException {
MyRunnable myRunnable = new MyRunnable();
// Start 3 threads
for (int i = 0; i < 3; i++) {
new Thread(myRunnable).start();
}
// Wait for all threads to finish
myRunnable.latch.await();
System.out.println("All threads have finished.");
}
}

In this example, we create a CountDownLatch with a count of 3. This means that the latch will only be counted down once 3 times (i.e., when each thread has finished its work). We then start 3 threads, which all sleep for 2 seconds and then print their status to the console. Finally, we use myRunnable.latch.await(); to wait until all threads have finished.

This example demonstrates how CountDownLatch can be used to synchronize multiple threads that are performing independent tasks but need to wait for each other to finish.

In Java 17, you would still be able to use CountDownLatch as per the above code. However, since Java 17 does not introduce any changes or limitations regarding CountDownLatch, you could also use it in earlier versions of Java like 14 and below.

In summary, CountDownLatch is a useful tool for managing threads and ensuring that they wait until certain operations are complete before proceeding.

What is CountDownLatch in Java?

A fundamental concept in Java concurrency!

CountDownLatch is a synchronization primitive introduced in Java 5 (part of the concurrency utilities package). It's a powerful tool for coordinating threads, particularly useful when dealing with tasks that require multiple threads to complete before allowing other threads to proceed.

At its core, CountDownLatch is a countdown counter that can be used to synchronize thread execution. The latch is initialized with a specified count value, which represents the number of threads waiting to be counted down. When a thread calls countDown() on the latch, it decrements the count by 1, effectively allowing one more thread to pass through the latch.

Here's how it works:

The benefits of using CountDownLatch:

Common use cases:

To illustrate the usage, consider a simple example:

CountDownLatch latch = new CountDownLatch(5);
// Register 5 threads to wait on the latch
for (int i = 0; i < 5; i++) {
new Thread(() -> {
// Simulate some task execution time
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Thread " + Thread.currentThread().getName() + " finished");
// Call countDown when the thread finishes its task
latch.countDown();
}).start();
}
// Wait for all threads to finish their tasks and release the latch
try {
latch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("All threads have completed!");

In this example, 5 threads are registered with the CountDownLatch, each simulating some task execution time. When a thread completes its task, it calls countDown() on the latch, allowing another thread to proceed. The main thread then waits for all threads to finish using await(), and when the count reaches 0, the program prints "All threads have completed!".

In summary, CountDownLatch is a powerful synchronization tool in Java that enables coordinating thread execution, ensuring dependencies between tasks are met, and facilitating decoupling of dependent threads.