public class CountTask extends RecursiveTask<Long> { 

//任务分解的阈值
private static final int THRESHOLD = 11;
private long start;
private long end;
public CountTask(long start, long end) { 

this.start = start;
this.end = end;
}
public Long compute() { 

long sum = 0;
boolean canCompute = (end - start) < THRESHOLD;
if (canCompute) { 

for (long i = start; i <= end; i++) { 

sum += i;
}
} else { 

//分成100个小任务
long step = (start + end) / 10;
ArrayList<CountTask> subTasks = new ArrayList<CountTask>();
long pos = start;
for (int i = 0; i < 10; i++) { 

long lastOne = pos + step;
if (lastOne > end) { 

lastOne = end;
}
CountTask subTask = new CountTask(pos, lastOne);
pos += step + 1;
//将子任务推向线程池
subTasks.add(subTask);
subTask.fork();
}
for (CountTask task : subTasks) { 

//对结果进行join
sum += task.join();
}
}
return sum;
}
public static void main(String[] args) throws ExecutionException, InterruptedException { 

ForkJoinPool pool = new ForkJoinPool();
// 累加求和 0 -> 100L
CountTask task = new CountTask(0, 100L);
ForkJoinTask<Long> result = pool.submit(task);
System.out.println("sum result : " + result.get());
}
}