Channel Directions in CLIPS

Channel directions in Java can be simulated using BlockingQueues, which provide thread-safe operations for adding and removing elements. We’ll use LinkedBlockingQueue to demonstrate this concept.

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

public class ChannelDirections {

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

    // The pong function 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 example, we use BlockingQueue<String> to simulate channel-like behavior. The LinkedBlockingQueue class provides thread-safe operations that block when the queue is full (for put()) or empty (for take()).

The ping function only accepts a queue for sending values. It uses the put() method to send a message.

The pong function accepts two queues: one for receiving (pings) and one for sending (pongs). It uses take() to receive a message from pings and put() to send it to pongs.

In the main method, we create two queues with a capacity of 1 to simulate unbuffered channels. We then call ping and pong in sequence, and finally print the received message.

To run the program:

$ javac ChannelDirections.java
$ java ChannelDirections
passed message

This example demonstrates how to simulate channel directions in Java using BlockingQueues. While Java doesn’t have built-in channel primitives like Go, the BlockingQueue interface provides similar functionality for inter-thread communication.