Timers in Squirrel

import java.util.Timer;
import java.util.TimerTask;

public class Timers {
    public static void main(String[] args) {
        // Timers represent a single event in the future. You
        // tell the timer how long you want to wait, and it
        // will execute a task at that time. This timer will wait 2 seconds.
        Timer timer1 = new Timer();
        timer1.schedule(new TimerTask() {
            @Override
            public void run() {
                System.out.println("Timer 1 fired");
            }
        }, 2000);

        // We use Thread.sleep to block the main thread until the timer fires.
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // If you just wanted to wait, you could have used
        // Thread.sleep. One reason a timer may be useful is
        // that you can cancel the timer before it fires.
        // Here's an example of that.
        Timer timer2 = new Timer();
        TimerTask task2 = new TimerTask() {
            @Override
            public void run() {
                System.out.println("Timer 2 fired");
            }
        };
        timer2.schedule(task2, 1000);

        boolean stop2 = task2.cancel();
        if (stop2) {
            System.out.println("Timer 2 stopped");
        }

        // Give the timer2 enough time to fire, if it ever
        // was going to, to show it is in fact stopped.
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // Make sure to cancel the timers to release resources
        timer1.cancel();
        timer2.cancel();
    }
}

In Java, we use the java.util.Timer and java.util.TimerTask classes to schedule tasks for future execution. Here’s how the example works:

We create a Timer object and schedule a TimerTask to run after 2 seconds. This is equivalent to the first timer in the original example.
We use Thread.sleep() to block the main thread until the timer fires. This is similar to the channel blocking in the original example.
For the second timer, we create another Timer and TimerTask, but this time we keep a reference to the task so we can cancel it.
We attempt to cancel the second timer using task2.cancel(). If successful, we print a message.
We use Thread.sleep() again to give the second timer time to fire if it wasn’t successfully cancelled.
Finally, we cancel both timers to release resources.

To run this program, save it as Timers.java, compile it with javac Timers.java, and then run it with java Timers.

The output should be:

Timer 1 fired
Timer 2 stopped

This demonstrates that the first timer fired after 2 seconds, but the second timer was successfully stopped before it had a chance to fire.

Note that Java’s Timer class is quite different from Go’s timer implementation. In Go, timers are closely tied to channels, while in Java, they work with TimerTask objects. The Java implementation also requires explicit cancellation of timers to release resources, which is handled automatically in Go.

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