Java ForkJoinPool getRunningThreadCount() Method

The getRunningThreadCount() method of ForkJoinPool class returns the number of thread that is currently running that are not blocked waiting to join tasks. This method may overestimate the number of running thread.

Syntax

Parameter

Returns

This method returns the number of worker threads.

Example 1

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveAction;
  class Task9 extends RecursiveAction {
     private long Load = 0;
 
 public Task9(long Load) {
         this.Load = Load;
    }
    @Override
    protected void compute() {
        //if work is above the threshold, break tasks up into smaller tasks
            List<Task9> subtasks = new ArrayList<Task9>();
                    subtasks.addAll(createSubtasks());
            for(RecursiveAction subtask : subtasks){
                subtask.fork();
            } 
    }

    private List<Task9> createSubtasks() {
        List<Task9> subtasks =new ArrayList<Task9>();

     Task9 subtask1 = new Task9(this.Load / 2);
     Task9 subtask2 = new Task9(this.Load / 2);
      Task9 subtask3 = new Task9(this.Load / 2);

        subtasks.add(subtask1);
        subtasks.add(subtask2);
        subtasks.add(subtask3);

        return subtasks;
    }

}
public class JavaForkJoingetActivethreadcountExample1 {

   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 = ForkJoinPool.commonPool();
      System.out.println(" Before invoking number of active thread   :" +Pool.getActiveThreadCount());
       Task9 t = new Task9(400);
       Pool.invoke(t); 
      System.out.println(" After invoking Numbers of active thread   :" +Pool.getActiveThreadCount());
      System.out.println("Common Pool Size   :" +Pool.getPoolSize());
   }  
}

Test it Now

Output:

numbers of core available in your processor:2
 Before invoking number of active thread   :0
 After invoking Numbers of active thread   :1
Common Pool Size   :1

Example 2

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

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

     Taskm subtask1 = new Taskm(this.Load / 2);
     Taskm subtask2 = new Taskm(this.Load / 2);
     Taskm subtask3 = new Taskm(this.Load / 2);
    
      
        subtasks.add(subtask1);
        subtasks.add(subtask2);
        subtasks.add(subtask3);
        
        
        return subtasks;
    }

}
public class JavaForkJoingetRunningthreadcountExample2 {

   public static void main(final String[] arguments) throws InterruptedException
      {      
      ForkJoinPool Pool = new ForkJoinPool(10);
       System.out.println(" Before invoking number of Running thread   :" +Pool.getRunningThreadCount());
       Taskm t = new Taskm(1000000);
       Pool.invoke(t);
       Pool.execute(t);
       System.out.println(" After invoking Numbers of Running thread   :" +Pool.getRunningThreadCount());
      System.out.println("Common Pool Size   :" +Pool.getPoolSize());
      
      
   }  
}

Test it Now

Output:

Before invoking number of Running thread   :0
 After invoking Numbers of Running thread   :10
Common Pool Size   :10

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