Signals in Miranda

Here’s the translation of the Go signals example to Java, formatted in Markdown suitable for Hugo:

Our program will demonstrate how to handle signals in Java. We’ll use a SignalHandler to gracefully handle termination signals like SIGINT (Ctrl+C) and SIGTERM.

import java.util.concurrent.CountDownLatch;
import sun.misc.Signal;
import sun.misc.SignalHandler;

public class SignalsExample {
    public static void main(String[] args) {
        // Create a CountDownLatch to wait for the signal
        CountDownLatch done = new CountDownLatch(1);

        // Register signal handlers for SIGINT and SIGTERM
        SignalHandler handler = signal -> {
            System.out.println();
            System.out.println(signal.getName());
            done.countDown();
        };

        Signal.handle(new Signal("INT"), handler);
        Signal.handle(new Signal("TERM"), handler);

        System.out.println("awaiting signal");

        try {
            // Wait for the signal
            done.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println("exiting");
    }
}

In this Java implementation:

1. We use sun.misc.Signal and sun.misc.SignalHandler to handle signals. Note that these classes are not part of the standard Java API and may not be available in all Java environments.

2. We create a CountDownLatch named done to synchronize the main thread with the signal handling thread.

3. We define a SignalHandler that prints the received signal’s name and counts down the latch.

4. We register this handler for both SIGINT and SIGTERM signals using Signal.handle().

5. The main thread waits on the CountDownLatch using done.await().

6. When a signal is received, the handler prints the signal name and counts down the latch, allowing the main thread to continue and exit.

When we run this program, it will block waiting for a signal. By typing ctrl-C (which the terminal shows as ^C), we can send a SIGINT signal, causing the program to print INT and then exit.

$ javac SignalsExample.java
$ java SignalsExample
awaiting signal
^C
INT
exiting

Note that signal handling in Java is not as straightforward as in some other languages, and the use of sun.misc.Signal is not recommended for production code as it’s not part of the standard API. For more robust signal handling in production environments, consider using alternative approaches such as shutdown hooks or JNI (Java Native Interface) to interact with system-level signal handling.