Worker Pools in CLIPS

import java.util.concurrent.*;

public class WorkerPools {

    // Here's the worker, of which we'll run several concurrent instances.
    // These workers will receive work on the `jobs` queue and send the
    // corresponding results on `results`. We'll sleep a second per job to
    // simulate an expensive task.
    static class Worker implements Runnable {
        private final int id;
        private final BlockingQueue<Integer> jobs;
        private final BlockingQueue<Integer> results;

        Worker(int id, BlockingQueue<Integer> jobs, BlockingQueue<Integer> results) {
            this.id = id;
            this.jobs = jobs;
            this.results = results;
        }

        public void run() {
            try {
                while (true) {
                    Integer j = jobs.take();
                    System.out.println("worker " + id + " started  job " + j);
                    Thread.sleep(1000); // Sleep for a second to simulate work
                    System.out.println("worker " + id + " finished job " + j);
                    results.put(j * 2);
                }
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        // In order to use our pool of workers we need to send them work
        // and collect their results. We create queues for this.
        final int numJobs = 5;
        BlockingQueue<Integer> jobs = new LinkedBlockingQueue<>();
        BlockingQueue<Integer> results = new LinkedBlockingQueue<>();

        // This starts up 3 workers, initially blocked because there are no jobs yet.
        ExecutorService executor = Executors.newFixedThreadPool(3);
        for (int w = 1; w <= 3; w++) {
            executor.submit(new Worker(w, jobs, results));
        }

        // Here we send 5 `jobs` and then `close` that queue to indicate
        // that's all the work we have.
        for (int j = 1; j <= numJobs; j++) {
            jobs.put(j);
        }
        executor.shutdown();

        // Finally we collect all the results of the work.
        // This also ensures that the worker threads have finished.
        for (int a = 1; a <= numJobs; a++) {
            results.take();
        }

        executor.awaitTermination(10, TimeUnit.SECONDS);
    }
}

This Java program demonstrates the implementation of a worker pool using threads and blocking queues. Here’s a breakdown of the key components:

We define a Worker class that implements Runnable. Each worker takes jobs from a jobs queue, processes them (simulated by sleeping for a second), and puts the results in a results queue.
In the main method, we create the jobs and results queues using LinkedBlockingQueue.
We create an ExecutorService with a fixed thread pool of 3 workers. This is equivalent to starting 3 goroutines in the Go example.
We submit 5 jobs to the jobs queue.
We shut down the executor service to signal that no more jobs will be submitted.
We collect the results from the results queue.
Finally, we wait for all workers to finish using awaitTermination.

To run this program, save it as WorkerPools.java, compile it with javac WorkerPools.java, and run it with java WorkerPools. The output will show the 5 jobs being executed by various workers, similar to the Go example.

This Java implementation uses threads and blocking queues to achieve similar functionality to the Go version with goroutines and channels. While the syntax and some concepts differ, the overall structure and purpose of the program remain the same.

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