Java ForkJoinPool hasQueuedSubmissions() Method

The hasQueuedSubmissions() method returns true if there are any tasks submitted to this pool that have not yet begun executing otherwise false.

Syntax

Parameter

Returns

This method returns a Boolean value true if there are any queued submissions.

Example 1

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveAction;
 class Workp extends RecursiveAction {
     private long Load = 0;
 
 public Workp(long Load) {
         this.Load = Load;
    }
    @Override
    protected void compute() {
        //if work is above the threshold, break tasks up into smaller tasks
        
            List<Workp> subtasks = new ArrayList<Workp>();
          
                subtasks.addAll(createSubtasks());
            
            for(RecursiveAction subtask : subtasks){
                subtask.fork();
            }
            
        
    }

    private List<Workp> createSubtasks() {
        List<Workp> subtasks =new ArrayList<Workp>();

     Workp subtask1 = new Workp(this.Load / 2);
    
      
        subtasks.add(subtask1);
        
        return subtasks;
    }

}
 public class JavaForkJoinhasQueuedSubmissionCountExample1 
 {

   public static void main(final String[] arguments) throws InterruptedException
      {      
      ForkJoinPool Pool = ForkJoinPool.commonPool();
      int i= Pool.getPoolSize();
      System.out.println("Has Queued Submission: " +Pool.hasQueuedSubmissions());
       Workp t = new Workp(1000);
       Pool.invoke(t);
       Pool.execute(t);
      
      
   }  
}

Test it Now

Output:

Has Queued Submission: false

Example 2

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

 public class JavaForkJoinhasQueuedSubmissionCountExample2 {

   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);
      Check t=new Check(n,0,n.length);
      
     System.out.println(" Before Queued Submission : " +Pool.hasQueuedSubmissions());
      System.out.println("  is awaitQuiescent : " + Pool.awaitQuiescence(2, TimeUnit.SECONDS) );
     Pool.awaitTermination(3, TimeUnit.SECONDS);
   System.out.println(" After Queued Submission : " +Pool.hasQueuedSubmissions());
      Integer r = Pool.invoke(t);
      System.out.println("Pool.invoke : " +r);
   }  
}

   class Check extends RecursiveTask<Integer> {
      int st;
      int end;
      int[] arr;

      Check(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;
            Check t1 = new Check(arr, st, mid);
            Check t2 = new Check(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 : false
  is awaitQuiescent : true
 After Queued Submission : false
Pool.invoke : 161

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