每分钟Java循环

我想在Java中编写一个第一个启动的循环，如下所示：

while (!x){ //wait one minute or two //execute code } 

我想这样做，以便它不会耗尽系统资源。 在代码中实际发生的是它进入一个网站并检查是否已完成某些事情，如果没有完成，它应该等待一分钟直到它再次检查，并且当它完成时它只是继续。 他们无论如何都要在java中这样做吗？

Answer 1

使用Thread.sleep(long millis) 。

导致当前正在执行的线程hibernate（暂时停止执行）指定的毫秒数，具体取决于系统计时器和调度程序的精度和准确性。 该线程不会失去任何监视器的所有权。

一分钟是(60*1000) = 60000毫秒。

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例如，此循环将每5秒打印一次当前时间：

  try { while (true) { System.out.println(new Date()); Thread.sleep(5 * 1000); } } catch (InterruptedException e) { e.printStackTrace(); } 

如果您的睡眠时间对于int来说太大，则显式计算为long （例如1000L ）。

Answer 2

你可以使用Timer

 Timer timer = new Timer(); timer.schedule( new TimerTask() { public void run() { // do your work } }, 0, 60*1000); 

什么时候到来

  timer.cancel(); 

关闭它。

Answer 3

 ScheduledExecutorService executor = Executors.newScheduledThreadPool(1); executor.schedule(yourRunnable, 1L, TimeUnit.MINUTES); ... // when done... executor.shutdown(); 

Answer 4

ScheduledExecutorService

李的答案很接近，但只运行一次。 该问题似乎要求无限期运行，直到外部状态发生变化（直到网站/服务的响应发生变化）。

ScheduledExecutorService接口是Java 5及更高版本java.util.concurrent内置的java.util.concurrent包的一部分，作为旧Timer类的更现代的替代品。

这是一个完整的例子。 调用scheduleAtFixedRate或scheduleWithFixedDelay 。

 ScheduledExecutorService executor = Executors.newScheduledThreadPool ( 1 ); Runnable r = new Runnable () { @Override public void run () { try { // Always wrap your Runnable with a try-catch as any uncaught Exception causes the ScheduledExecutorService to silently terminate. System.out.println ( "Now: " + Instant.now () ); // Our task at hand in this example: Capturing the current moment in UTC. if ( Boolean.FALSE ) { // Add your Boolean test here to see if the external task is fonud to be completed, as described in this Question. executor.shutdown (); // 'shutdown' politely asks ScheduledExecutorService to terminate after previously submitted tasks are executed. } } catch ( Exception e ) { System.out.println ( "Oops, uncaught Exception surfaced at Runnable in ScheduledExecutorService." ); } } }; try { executor.scheduleAtFixedRate ( r , 0L , 5L , TimeUnit.SECONDS ); // ( runnable , initialDelay , period , TimeUnit ) Thread.sleep ( TimeUnit.MINUTES.toMillis ( 1L ) ); // Let things run a minute to witness the background thread working. } catch ( InterruptedException ex ) { Logger.getLogger ( App.class.getName () ).log ( Level.SEVERE , null , ex ); } finally { System.out.println ( "ScheduledExecutorService expiring. Politely asking ScheduledExecutorService to terminate after previously submitted tasks are executed." ); executor.shutdown (); } 

预期输出如下：

 Now: 2016-12-27T02:52:14.951Z Now: 2016-12-27T02:52:19.955Z Now: 2016-12-27T02:52:24.951Z Now: 2016-12-27T02:52:29.951Z Now: 2016-12-27T02:52:34.953Z Now: 2016-12-27T02:52:39.952Z Now: 2016-12-27T02:52:44.951Z Now: 2016-12-27T02:52:49.953Z Now: 2016-12-27T02:52:54.953Z Now: 2016-12-27T02:52:59.951Z Now: 2016-12-27T02:53:04.952Z Now: 2016-12-27T02:53:09.951Z ScheduledExecutorService expiring. Politely asking ScheduledExecutorService to terminate after previously submitted tasks are executed. Now: 2016-12-27T02:53:14.951Z