A recursive result-bearing `ForkJoinTask`.

For a classic example, here is a task computing Fibonacci numbers:

``` ```class Fibonacci extends RecursiveTask<Integer> {
final int n;
Fibonacci(int n) { this.n = n; }
protected Integer compute() {
if (n <= 1)
return n;
Fibonacci f1 = new Fibonacci(n - 1);
f1.fork();
Fibonacci f2 = new Fibonacci(n - 2);
return f2.compute() + f1.join();
}
}``````
However, besides being a dumb way to compute Fibonacci functions (there is a simple fast linear algorithm that you'd use in practice), this is likely to perform poorly because the smallest subtasks are too small to be worthwhile splitting up. Instead, as is the case for nearly all fork/join applications, you'd pick some minimum granularity size (for example 10 here) for which you always sequentially solve rather than subdividing.

### Public Method Summary

 final V getRawResult() Returns the result that would be returned by `join()`, even if this task completed abnormally, or `null` if this task is not known to have been completed.

### Protected Method Summary

 abstract V compute() The main computation performed by this task. final boolean exec() Implements execution conventions for RecursiveTask. final void setRawResult(V value) Forces the given value to be returned as a result.

## Public Methods

#### public final V getRawResult()

Returns the result that would be returned by `join()`, even if this task completed abnormally, or `null` if this task is not known to have been completed. This method is designed to aid debugging, as well as to support extensions. Its use in any other context is discouraged.

##### Returns
• the result, or `null` if not completed

## Protected Methods

#### protected abstract V compute()

The main computation performed by this task.

##### Returns
• the result of the computation

#### protected final boolean exec()

• `true` if this task is known to have completed normally