On Thu, 20 May 2021 10:16:28 GMT, Tagir F. Valeev <tval...@openjdk.org> wrote:
> Sometimes, `Spliterator::forEachRemaining` has much more optimized > implementation, compared to `Spliterator::tryAdvance`. For example, if a > `Stream::spliterator` called for a stream that has intermediate operations, > `tryAdvance()` may buffer intermediate elements while `forEachRemaining()` > just delegates to the `wrapAndCopyInto` (see > `StreamSpliterators.AbstractWrappingSpliterator` and its inheritors). > > `Spliterators::iterator` methods (used in particular by `Stream::iterator`) > provide adapter iterators that delegate to the supplied spliterator. > Unfortunately, they don't have a specialized implementation for > `Iterator::forEachRemaining`. As a result, a default implementation is used > that delegates to `hasNext`/`next`, which in turn causes the delegation to > `tryAdvance`. It's quite simple to implement `Iterator::forEachRemaining` > here, taking advantage of possible spliterator optimizations if the iterator > client decides to use `forEachRemaining`. > > This patch implements Iterator::forEachRemaining in Spliterators::iterator > methods. Also, I nullize the `nextElement` in `Iterator::next` to avoid > accidental prolongation of the user's object lifetime when iteration is > finished. Finally, a small cleanup: I added the `final` modifier where > possible to private fields in `Spliterators`. > > Test-wise, some scenarios are already covered by > SpliteratorTraversingAndSplittingTest. However, the resulting iterator is > always wrapped into `Spliterators::spliterator`, so usage scenarios are > somewhat limited. In particular, calling `hasNext` (without `next`) before > `forEachRemaining` was not covered there. I added more tests in > `IteratorFromSpliteratorTest` to cover these scenarios. I checked that > removing `valueReady = false;` or `action.accept(t);` lines from newly > implemented `forEachRemaining` method causes new tests to fail (but old tests > don't fail due to this). This pull request has now been integrated. Changeset: ac36b7d3 Author: Tagir F. Valeev <tval...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/ac36b7d3e2d521652576fba3b1760586f582544f Stats: 198 lines in 2 files changed: 193 ins; 0 del; 5 mod 8267452: Delegate forEachRemaining in Spliterators.iterator() Reviewed-by: psandoz ------------- PR: https://git.openjdk.java.net/jdk/pull/4124
