Channel Directions in Minitab

In Java, we can use the BlockingQueue interface to achieve similar functionality to Go’s channels. The BlockingQueue interface is part of the java.util.concurrent package and provides thread-safe operations for adding and removing elements.

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

public class ChannelDirections {

    // This ping method only accepts a queue for sending values.
    // It would be a compile-time error to try to receive from this queue.
    public static void ping(BlockingQueue<String> pings, String msg) throws InterruptedException {
        pings.put(msg);
    }

    // The pong method accepts one queue for receives (pings) and a second for sends (pongs).
    public static void pong(BlockingQueue<String> pings, BlockingQueue<String> pongs) throws InterruptedException {
        String msg = pings.take();
        pongs.put(msg);
    }

    public static void main(String[] args) throws InterruptedException {
        BlockingQueue<String> pings = new LinkedBlockingQueue<>(1);
        BlockingQueue<String> pongs = new LinkedBlockingQueue<>(1);

        ping(pings, "passed message");
        pong(pings, pongs);
        System.out.println(pongs.take());
    }
}

In this Java version:

1. We use BlockingQueue<String> instead of channels. The BlockingQueue interface provides methods like put() for sending and take() for receiving, which block if the queue is full or empty respectively.

2. The ping method takes a BlockingQueue<String> for sending messages. It uses the put() method to send a message.

3. The pong method takes two BlockingQueue<String> objects: one for receiving (pings) and one for sending (pongs). It uses take() to receive a message and put() to send it.

4. In the main method, we create two LinkedBlockingQueue instances with a capacity of 1 to mimic the behavior of the Go channels.

5. We call ping and pong methods, and then print the result from the pongs queue.

To run this program:

$ javac ChannelDirections.java
$ java ChannelDirections
passed message

This Java implementation provides similar functionality to the Go example, using BlockingQueue to manage concurrent communication between threads. While it’s not an exact match to Go’s channel directions, it demonstrates how to achieve similar behavior in Java.