Java forkJoinPool getPoolSize() Method

The getPoolSize() method of ForkJoinPool class is used to get the size of the pool. Size of the pool depends on the number of workers that have started but not yet terminated.

Syntax

Parameter

No parameter is passed.

Returns

The number of worker threads.

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

    private List<Work> createSubtasks() {
        List<Work> subtasks =new ArrayList<Work>();
       Work subtask1 = new Work(this.Load / 2);
        subtasks.add(subtask1);
        return subtasks;
   }
}
public class JavaForkJoingetPoolSizeExample1 
 {
   public static void main(final String[] arguments) throws InterruptedException
      {      
      ForkJoinPool Pool = ForkJoinPool.commonPool();
      int i= Pool.getPoolSize();
      System.out.println("Common Pool Size before  :" +i);
       Work t = new Work(1000);
       Pool.invoke(t);
      System.out.println("Common Pool Size after  :" +Pool.getPoolSize());
       }  
}

Test it Now

Output:

Common Pool Size before  :0
Common Pool Size after  :1

Example 2

           import java.util.concurrent.ForkJoinPool;
           import java.util.concurrent.RecursiveTask;
           public class JavaForkJoingetPoolSizeExample2 extends RecursiveTask<Integer> {
               @Override
              protected Integer compute() {
                  try{
                       throw new UnsupportedOperationException("Not supported yet."); //To change body of //generated methods, choose Tools | Templates.
                  }
                  catch(Exception e)
                  { 
                  }
                  return 0;
               }
               public static void main(String[] args) {
	      JavaForkJoingetPoolSizeExample2 left = new JavaForkJoingetPoolSizeExample2();
             JavaForkJoingetPoolSizeExample2 right = new JavaForkJoingetPoolSizeExample2();
             JavaForkJoingetPoolSizeExample2 finder = new JavaForkJoingetPoolSizeExample2();
             ForkJoinPool pool = ForkJoinPool.commonPool();
           pool.submit(left); pool.submit(right); pool.submit(finder);
           System.out.println(" Pool Size :" +pool.getPoolSize());
	  }
        }

Test it Now

Output: