Java forkJoinPool getQueuedTaskCount() Method

The getQueuedTaskCount() method of ForkJoinPool class is used to get the estimation of the number of tasks in the working queue. This does not include tasks which are yet to be executed.

Syntax

Parameter

Returns

The number of queued tasks

Throws

Does not throw the exception.

Example 1

import java.util.concurrent.ForkJoinPool;
import static java.util.concurrent.ForkJoinTask.invokeAll;
import java.util.concurrent.RecursiveTask;
import java.util.concurrent.TimeUnit;
public class JavaForkJoingetQueuedTaskCountExample1  {
  public static void main(final String[] arguments) throws InterruptedException
      {
      int proc = Runtime.getRuntime().availableProcessors();
      System.out.println("numbers of core available in your processor:"  +proc);
      int[] n = {20 , 23 , 5 ,6 ,7,8,23,12,56,1}; 
      ForkJoinPool Pool = new ForkJoinPool(proc);
      Tests t=new Tests(n,0,n.length);
      System.out.println("  is Quiescent :" + Pool.awaitQuiescence(2, TimeUnit.SECONDS) );
       System.out.println(" queued task count :" + Pool.getQueuedTaskCount() );
      ForkJoinPool.commonPool().awaitQuiescence(2, TimeUnit.SECONDS);
      Integer r = Pool.invoke(t);
      System.out.println("Pool.invoke :" +r);
      }  
}

   class Tests extends RecursiveTask<Integer> {
      int st;
      int end;
      int[] arr;
    Tests(int[] arr, int st, int end) {
         this.arr = arr;
         this.st  = st;
         this.end  = end;
      }
      protected Integer compute() {
            if(st - end <= 10) {
            int sum = 0;
            for(int i = st; i < end; ++i) 
               sum += arr[i];
              return sum;
         } else {	    	
            int mid = st + (end - st) / 2;
            Tests t1 = new Tests(arr, st, mid);
            Tests t2 = new Tests(arr, st, mid);
            invokeAll(t1 , t2);
            return (t1.join() + t2.join());
         }
      }
   }

Test it Now

Output:

numbers of core available in your processor:4
  is Quiescent :true
 queued task count :0
Pool.invoke :161

Example 2

import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask.*;
import java.util.concurrent.RecursiveTask;
import java.util.concurrent.TimeUnit;


public class JavaForkJoingetQueuedTaskCountExample2 {

   public static void main(final String[] arguments) throws InterruptedException
      {
      
      int proc = Runtime.getRuntime().availableProcessors();
      System.out.println("numbers of core available in your processor:"  +proc);
      ForkJoinPool Pool = new ForkJoinPool(proc);
      Testt2 t=new Testt2();
     System.out.println(" queued task count :" + Pool.getQueuedTaskCount() );
      
   }  
}

   class Testt2 extends RecursiveTask<Integer> {
    @Override
      protected Integer compute() {
            Testt2 t1 = new Testt2();
            Testt2 t2 = new Testt2();
            invokeAll(t1 , t2);
            return (t1.join() + t2.join());
         }
      }

Test it Now

Output:

numbers of core available in your processor:4
 queued task count :0

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