Channel Synchronization in Squirrel

Channel synchronization in Java can be achieved using various concurrency utilities. Here’s an example using a CountDownLatch to wait for a thread to finish.

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

public class ChannelSynchronization {

    // This is the method we'll run in a separate thread. The
    // CountDownLatch will be used to notify the main thread
    // that this method's work is done.
    static void worker(CountDownLatch latch) {
        System.out.print("working...");
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("done");

        // Count down to notify that we're done.
        latch.countDown();
    }

    public static void main(String[] args) throws InterruptedException {
        // Create a CountDownLatch with a count of 1
        CountDownLatch latch = new CountDownLatch(1);

        // Start a worker thread, giving it the latch to notify on.
        new Thread(() -> worker(latch)).start();

        // Block until we receive a notification from the
        // worker thread via the latch.
        latch.await();
    }
}

To run the program:

$ javac ChannelSynchronization.java
$ java ChannelSynchronization
working...done

If you removed the latch.await() line from this program, the main thread would exit before the worker thread even started its work.

In this Java version:

1. We use a CountDownLatch instead of a channel. The CountDownLatch allows one or more threads to wait until a set of operations being performed in other threads completes.

2. The worker method is now a static method that takes a CountDownLatch as an argument.

3. Instead of using a goroutine, we create a new Thread and start it.

4. The latch.countDown() call in the worker method is equivalent to sending a value on the channel in the Go version.

5. The latch.await() call in the main method is equivalent to receiving from the channel in the Go version. It blocks until the latch has counted down to zero.

This example demonstrates how to synchronize execution between threads in Java, which is conceptually similar to synchronizing goroutines with channels in Go.