Non Blocking Channel Operations in Squirrel

Java provides several ways to implement non-blocking operations, including the use of ExecutorService and Future. Here’s an example that demonstrates non-blocking operations similar to the original code:

import java.util.concurrent.*;

public class NonBlockingOperations {
    public static void main(String[] args) {
        ExecutorService executor = Executors.newSingleThreadExecutor();
        BlockingQueue<String> messages = new LinkedBlockingQueue<>();
        BlockingQueue<Boolean> signals = new LinkedBlockingQueue<>();

        // Here's a non-blocking receive. If a value is
        // available in `messages`, it will be retrieved.
        // If not, it will immediately take the `else` branch.
        try {
            String msg = messages.poll();
            if (msg != null) {
                System.out.println("received message " + msg);
            } else {
                System.out.println("no message received");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        // A non-blocking send works similarly. Here `msg`
        // is offered to the `messages` queue. If the queue
        // is full, it will immediately take the `else` branch.
        String msg = "hi";
        try {
            if (messages.offer(msg)) {
                System.out.println("sent message " + msg);
            } else {
                System.out.println("no message sent");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        // We can use multiple `Future`s to implement a multi-way
        // non-blocking select. Here we attempt non-blocking receives
        // on both `messages` and `signals`.
        Future<String> messageFuture = executor.submit(() -> messages.poll(100, TimeUnit.MILLISECONDS));
        Future<Boolean> signalFuture = executor.submit(() -> signals.poll(100, TimeUnit.MILLISECONDS));

        try {
            String receivedMsg = messageFuture.get(1, TimeUnit.MILLISECONDS);
            if (receivedMsg != null) {
                System.out.println("received message " + receivedMsg);
            } else {
                Boolean receivedSignal = signalFuture.get(1, TimeUnit.MILLISECONDS);
                if (receivedSignal != null) {
                    System.out.println("received signal " + receivedSignal);
                } else {
                    System.out.println("no activity");
                }
            }
        } catch (TimeoutException e) {
            System.out.println("no activity");
        } catch (Exception e) {
            e.printStackTrace();
        }

        executor.shutdown();
    }
}

This Java code demonstrates non-blocking operations using ExecutorService, Future, and BlockingQueue.

We create an ExecutorService and two BlockingQueues for messages and signals.
For the non-blocking receive, we use the poll() method of BlockingQueue, which immediately returns null if the queue is empty.
For the non-blocking send, we use the offer() method, which returns false if the message couldn’t be added to the queue immediately.
To implement a multi-way non-blocking select, we use Futures. We submit tasks to the ExecutorService to poll from both queues with a short timeout. We then use Future.get() with a very short timeout to check the results non-blockingly.

When you run this program, you’ll see output similar to:

$ java NonBlockingOperations
no message received
no message sent
no activity

This example demonstrates how to perform non-blocking operations in Java, which can be useful in scenarios where you want to check for data availability without blocking the execution of your program.

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Non Blocking Channel Operations in Squirrel