`ScheduledExecutorService`

Question

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，以免它耗尽系统资源。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)。

使当前正在执行的线程休眠（暂时停止执行）指定的毫秒数，具体取决于系统定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。

一分钟为(60*1000) = 60000毫秒。

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而言过大，请在long中明确计算（例如1000L）。

Answer 2

您可以使用Timer

Timer timer = new Timer();

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

时机成熟

  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`

Answer by Lee已关闭，但只运行一次。该问题似乎要求无限期地运行，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中内置的java.util.concurrent包的一部分，后来作为旧Timer类的更现代的替代。

这是一个完整的例子。致电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

Answer 5

如果您使用的是 SpringBoot 应用程序，那就很简单了

预定流程

@Log
@Component
public class ScheduledProcess {

    @Scheduled(fixedRate = 5000)
    public void run() {
        log.info("this runs every 5 seconds..");
    }

}

Application.class

@SpringBootApplication
// ADD THIS ANNOTATION TO YOUR APPLICATION CLASS
@EnableScheduling
public class SchedulingTasksApplication {

    public static void main(String[] args) {
        SpringApplication.run(SchedulingTasksApplication.class);
    }
}

每分钟Java循环

5 个答案:

`ScheduledExecutorService`