Java forkJoinPool getQueuedSubmissionCount() Method

The getQueuedSubmissionCount() method of ForkJoinPool class is used to get the number of tasks submitted to the pool but yet to be executed.

Syntax

Parameter

Returns

The number of queued submissions

Throws

Does not throw the Exception.

Example 1

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveAction;
 class Work1 extends RecursiveAction {
     private long Load = 0;
 public Work1(long Load) {
         this.Load = Load;
    }
    @Override
    protected void compute() {
        //if work is above threshold, break tasks up into smaller tasks
            List<Work1> subtasks = new ArrayList<Work1>();
                subtasks.addAll(createSubtasks());
            for(RecursiveAction subtask : subtasks){
                subtask.fork();
            }
    }
    private List<Work1> createSubtasks() {
        List<Work1> subtasks =new ArrayList<Work1>();
     Work1 subtask1 = new Work1(this.Load / 2);
        subtasks.add(subtask1);
        
        return subtasks;
    }
}
public class JavaForkJoingetQueuedSubmissionCountExample1 
 {
   public static void main(final String[] arguments) throws InterruptedException
      {      
      ForkJoinPool Pool = ForkJoinPool.commonPool();
      int i= Pool.getPoolSize();
      System.out.println("Queued Submission  :" +Pool.getQueuedSubmissionCount());
       Work1 t = new Work1(1000);
       Pool.invoke(t);
       Pool.execute(t);   
   }  
}

Test it Now

Output:

Queued Submission  :0

Example 2

import java.util.concurrent.ForkJoinPool;
import static java.util.concurrent.ForkJoinTask.invokeAll;
import java.util.concurrent.RecursiveTask;
import java.util.concurrent.TimeUnit;
public class JavaForkJoingetQueuedSubmissionCountExample2 {
   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);
      Test2 t=new Test2(n,0,n.length);
     System.out.println(" Before Queued Submission  :" +Pool.getQueuedSubmissionCount());
      System.out.println("  is awaitQuiescent :" + Pool.awaitQuiescence(2, TimeUnit.SECONDS) );
     Pool.awaitTermination(3, TimeUnit.SECONDS);
   System.out.println(" After Queued Submission  :" +Pool.getQueuedSubmissionCount());
      Integer r = Pool.invoke(t);
      System.out.println("Pool.invoke :" +r);
   }  
}
   class Test2 extends RecursiveTask<Integer> {
      int st;
      int end;
      int[] arr;
    Test2(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;
            Test2 t1 = new Test2(arr, st, mid);
            Test2 t2 = new Test2(arr, st, mid);
            invokeAll(t1 , t2);
             return (t1.join() + t2.join());
         }
      }
   }

Test it Now

Output:

numbers of core available in your processor:4
 Before Queued Submission  :0
  is awaitQuiescent :true
 After Queued Submission  :0
Pool.invoke :161

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