Question

是否可以使ScheduledExecutorService具有一个正在运行的任务且只有一个等待任务？

  Runnable runnable;
  ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
  private volatile ScheduledFuture<?> self;

 protected void waitAndSweep(final String symbol) {
    try { 

        runnable = new Runnable() {
          @Override
          public void run() {
            try {
              long sweepTime = symbolInfo.getSweepTime(symbol);
              long timeSinceLastSweep = System.currentTimeMillis() - sweepTime;
              long waitTime = timeSinceLastSweep >= getInterval() ? 0 : getInterval() - timeSinceLastSweep;
              logTradeEvent("waitAndSweep", symbol, "waittime: " + waitTime);
              if (waitTime > 0){
                Thread.sleep(waitTime);
              }
              callSweep(symbol);
            } catch (Exception e) {
              // TODO Auto-generated catch block
              e.printStackTrace();
            }            
          }
        };

      self = scheduler.schedule(runnable,0,TimeUnit.SECONDS);


    }catch (Exception e) {
      logEvent(StrategyEntry.ERROR, "waitAndSweep", symbol,
          "Exception caught...", e);
    }
  }

在上面的代码中，假设一个可运行的任务由调度程序调度，它正在等待10s（thread.sleep（time）），在这个休眠时间内，如果调度程序安排了其他任务，它将等待。现在第三个任务进入调度程序，然后调度程序不应该接受它，因为已经有一个正在运行和一个等待任务

Answer 1

您需要使用ScheduledExecutorService还是ThreadPoolExecutor？如果是这样，您可以通过自己创建（而不是使用Executors.newFixedThreadPool（1））来控制一次排队的任务数量，并为您自己的队列提供如下定义的容量：

var re = /<br>([^<]*>)/gi; 
var str = '<span style="font-family:Arial;font-size: 14px;">\n   <span class="author-basic">new op\n        <span style="font-size: 30px;">tionlab</span> \n   </span<br>>';
var subst = '$1<br>'; 
var result = str.replace(re, subst);
alert(result);

此外，您可以使用Spring框架中的ThreadPoolTaskExecutor类以较少的配置执行此操作：

  int  oneThread       = 1;
  long zeroKeepAlive   = 0L;
  int  queueDepthOfOne = 1;

  ThreadPoolExecutor threadPoolExecutor =
        new ThreadPoolExecutor(
              oneThread,
              oneThread,
              zeroKeepAlive,
              TimeUnit.MILLISECONDS,
              new ArrayBlockingQueue<Runnable>(queueDepthOfOne)
        );

ThreadPoolTaskExecutor API文档：http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/scheduling/concurrent/ThreadPoolTaskExecutor.html

ScheduledExecutorService和计划的行为

1 个答案: