ExecutorService中的活动线程

任何想法如何确定在ExecutorService中运行的活动线程的数量？

Answer 1

使用ThreadPoolExecutor实现并调用getActiveCount（） ：

int getActiveCount() // Returns the approximate number of threads that are actively executing tasks. 

ExecutorService接口不提供一个方法，这取决于实现。

Answer 2

检查Executors.newFixedThreadPool（）的源代码：

 return new ThreadPoolExecutor(nThreads, nThreads, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>()); 

ThreadPoolExecutor有一个getActiveCount（）方法。 所以你可以将ExecutorService转换为ThreadPoolExecutor，或者直接使用上面的代码来获得一个。 然后你可以调用getActiveCount（）。

Answer 3

假定pool是ExecutorService实例的名称：

 if (pool instanceof ThreadPoolExecutor) { System.out.println( "Pool size is now " + ((ThreadPoolExecutor) pool).getActiveCount() ); } 

Answer 4

ExecutorService接口没有定义一个方法来检查池中工作线程的数量，因为这是一个实现细节

 public int getPoolSize() Returns the current number of threads in the pool. 

在ThreadPoolExecutor类中可用

 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;


公共类PoolSize {

     public static void main（String [] args）{
         ThreadPoolExecutor executor = new ThreadPoolExecutor（10，20，60L，TimeUnit.SECONDS，new LinkedBlockingQueue（））;
        的System.out.println（executor.getPoolSize（））;
     }
 }

但是这需要你显式地创buildThreadPoolExecutor，而不是使用返回ExecutorService对象的Executors工厂。 你总是可以创build自己的返回ThreadPoolExecutors的工厂，但是仍然会留下使用具体types的错误forms，而不是它的接口。

一种可能性是提供自己的ThreadFactory，它在已知的线程组中创build线程，然后您可以进行计数

 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ThreadFactory;


公共类PoolSize2 {

     public static void main（String [] args）{
         final ThreadGroup threadGroup = new ThreadGroup（“workers”）;

         ExecutorService executor = Executors.newCachedThreadPool（new ThreadFactory（）{
            公共线程newThread（Runnable r）{
                返回新的线程（threadGroup，r）;
             }
         }）;

        的System.out.println（threadGroup.activeCount（））;
     }
 }

Answer 5

我有同样的问题，所以创build了一个简单的Runnable来跟踪一个ExecutorService实例。

 import java.util.concurrent.ExecutorService; import java.util.concurrent.ThreadPoolExecutor; public class ExecutorServiceAnalyzer implements Runnable { private final ThreadPoolExecutor threadPoolExecutor; private final int timeDiff; public ExecutorServiceAnalyzer(ExecutorService executorService, int timeDiff) { this.timeDiff = timeDiff; if (executorService instanceof ThreadPoolExecutor) { threadPoolExecutor = (ThreadPoolExecutor) executorService; } else { threadPoolExecutor = null; System.out.println("This executor doesn't support ThreadPoolExecutor "); } } @Override public void run() { if (threadPoolExecutor != null) { do { System.out.println("#### Thread Report:: Active:" + threadPoolExecutor.getActiveCount() + " Pool: " + threadPoolExecutor.getPoolSize() + " MaxPool: " + threadPoolExecutor.getMaximumPoolSize() + " ####"); try { Thread.sleep(timeDiff); } catch (Exception e) { } } while (threadPoolExecutor.getActiveCount() > 1); System.out.println("##### Terminating as only 1 thread is active ######"); } } } 

你可以简单地用你的执行器来获取ThreadPool的状态

防爆

 ExecutorService executorService = Executors.newFixedThreadPool(4); executorService.execute(new ExecutorServiceAnalyzer(executorService, 1000)); 

Answer 6

在线程中放置一个静态易失性计数器，每当线程被激活和closures时都会更新。 另请参阅API。