Closing Channels in Minitab

In Java, we don’t have direct equivalents for channels and goroutines. However, we can simulate similar behavior using threads and blocking queues. Here’s how we can translate the concept of closing channels:

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;

public class ClosingChannels {
    public static void main(String[] args) throws InterruptedException {
        BlockingQueue<Integer> jobs = new LinkedBlockingQueue<>(5);
        BlockingQueue<Boolean> done = new LinkedBlockingQueue<>();

        // Here's the worker thread. It repeatedly takes from 'jobs'.
        // We use a special sentinel value (null) to indicate that no more jobs will be sent.
        Thread worker = new Thread(() -> {
            while (true) {
                try {
                    Integer j = jobs.take();
                    if (j != null) {
                        System.out.println("received job " + j);
                    } else {
                        System.out.println("received all jobs");
                        done.put(true);
                        return;
                    }
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                    return;
                }
            }
        });
        worker.start();

        // This sends 3 jobs to the worker over the 'jobs' queue, then sends a null to indicate completion.
        for (int j = 1; j <= 3; j++) {
            jobs.put(j);
            System.out.println("sent job " + j);
        }
        jobs.put(null);
        System.out.println("sent all jobs");

        // We await the worker using the synchronization approach.
        done.take();

        // In Java, we don't have a direct equivalent to checking if a channel is closed.
        // Instead, we can check if the queue is empty after we've sent all jobs.
        System.out.println("jobs queue is empty: " + jobs.isEmpty());
    }
}

This Java code simulates the behavior of the original example. Here’s a breakdown of the changes:

We use BlockingQueue<Integer> instead of a channel for jobs. This allows us to send and receive jobs in a thread-safe manner.
Instead of closing the channel, we send a special sentinel value (null) to indicate that no more jobs will be sent.
The worker thread continuously takes jobs from the queue until it receives the sentinel value.
We use a BlockingQueue<Boolean> for done to signal when all jobs have been processed.
Instead of using the special 2-value form of receive that Go channels have, we simply check if the received value is null to determine if there are more jobs.
The main thread puts jobs into the queue and then waits for the worker to finish by taking from the done queue.
At the end, we check if the jobs queue is empty, which is analogous to checking if more values can be received from a closed channel in Go.

To run this program:

$ javac ClosingChannels.java
$ java ClosingChannels
sent job 1
received job 1
sent job 2
received job 2
sent job 3
received job 3
sent all jobs
received all jobs
jobs queue is empty: true

This example demonstrates how to simulate channel-like behavior in Java using blocking queues and threads. While it’s not an exact translation, it captures the essence of the original Go code’s functionality.

Non Blocking Channel Operations in Minitab

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Closing Channels in Minitab