StackOverflow2013

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POCreate a java thread that runs on a timer but can be awaken at any time
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copied!<p>I would like to create a class that runs something (a runnable) at regular intervals but that can be awaken when needed. If I could encapsulate the whole thing I would like to expose the following methods:</p> <pre><code>public class SomeService implements Runnable { public run() { // the code to run at every interval } public static void start() { } public static void wakeup() { } public static void shutdown() { } } </code></pre> <p>Somehow I've gotten this far. But I'm not sure if this is the correct approach.</p> <pre><code>public class SomeService implements Runnable { private static SomeService service; private static Thread thread; static { start(); } private boolean running = true; private SomeService() { } public void run() { while (running) { try { // do what needs to be done // perhaps peeking at a blocking queue // or checking for records in a database // trying to be independent of the communication System.out.println("what needs to be done"); // wait for 15 seconds or until notify synchronized (thread) { try { thread.wait(15000); } catch (InterruptedException e) { System.out.println("interrupted"); } } } catch (Exception e) { e.printStackTrace(); } } } private static void start() { System.out.println("start"); service = new SomeService(); thread = new Thread(service); thread.setDaemon(true); thread.start(); } public static void wakeup() { synchronized (thread) { thread.notify(); } } public static void shutdown() { synchronized (thread) { service.running = false; thread.interrupt(); try { thread.join(); } catch (InterruptedException e) { e.printStackTrace(); } } System.out.println("shutdown"); } public static void main(String[] args) throws IOException { SomeService.wakeup(); System.in.read(); SomeService.wakeup(); System.in.read(); SomeService.shutdown(); } } </code></pre> <p>I'm concerned that the variables should be declared volatile. And also concerned that I should check in the "what needs to be done part" for <code>thread.isInterrupted()</code>. Does this seem like the right approach? Should I translate this to executors? How can I force a run on a scheduled executor?</p> <p>EDIT</p> <p>After experimenting with the executor, it seems that this approach seems reasonable. What do you think?</p> <pre><code>public class SomeExecutorService implements Runnable { private static final SomeExecutorService runner = new SomeExecutorService(); private static final ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor(); // properties ScheduledFuture<?> scheduled = null; // constructors private SomeExecutorService() { } // methods public void schedule(int seconds) { scheduled = executor.schedule(runner, seconds, TimeUnit.SECONDS); } public void force() { if (scheduled.cancel(false)) { schedule(0); } } public void run() { try { _logger.trace("doing what is needed"); } catch (Exception e) { _logger.error("unexpected exception", e); } finally { schedule(DELAY_SECONDS); } } // static methods public static void initialize() { runner.schedule(0); } public static void wakeup() { runner.force(); } public static void destroy() { executor.shutdownNow(); } } </code></pre>

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