Java ForkJoinPool getUncaughtExceptionHandler() Method

The getUncaughtExceptionHandler() method of ForkJoinPool class returns the exception handler for internal worker threads that terminate due to an unrecoverable error.

Syntax

Parameter

Returns

This method returns the handler or null if none.

Example 1

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

public class GetUncaughtExceptionHandlerExample1  {

   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);
      Testm t=new Testm(n,0,n.length);
      System.out.println("  Exception Handler : " +Pool.getUncaughtExceptionHandler() );
      ForkJoinPool.commonPool().awaitQuiescence(2, TimeUnit.SECONDS);
    
      Integer r = Pool.invoke(t);
      System.out.println("Pool.invoke :" +r); 
   }  
}

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

      Testm(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;
            Testm t1 = new Testm(arr, st, mid);
            Testm t2 = new Testm(arr, st, mid);
            invokeAll(t1 , t2);
             
            return (t1.join() + t2.join());
         }
      }
   }

Test it Now

Output:

numbers of core available in your processor:2
  Exception Handler : null
Pool.invoke :161

Example 2

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

            for(RecursiveAction subtask : subtasks){
                subtask.fork();
            }
    }

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

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

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

        return subtasks;
    }
}
public class GetUncaughtExceptionHandlerExample2 {

   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();
      int i= Pool.getPoolSize();
      System.out.println("uncaught exception handler : " +Pool.getUncaughtExceptionHandler());
       Taskl t = new Taskl(400);
       Pool.invoke(t);
        
   }  
}

Test it Now

Output:

numbers of core available in your processor:4
uncaught exception handler : null

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