On Sat, 8 Apr 2023 23:18:04 GMT, Chen Liang <li...@openjdk.org> wrote:
>> In the current implementation of `String.join(CharSequence, Iterable)`, the >> temp array `elems` is always initialized with a length of 8. It will cause >> many array recreations when the `Iterable` contains more than 8 elements. >> Furthermore, it's very common that an `Iterable` is also a `Collection`. So >> if the `Iterable` is an instance of `Collection`, the initial length of the >> array can be `((Collection<?>)elements).size()`. It will not change the >> current behavior even if the `Collection` is modified asynchronously. >> >> I don't know whether this change requires a CSR request. > > Have you considered the performance impact on concurrent collections, that > their size() computation is non-constant, and the array still may need > resizing later (which you've kept, good) @liach Thanks for reminding that. Some collections such as `java.util.concurrent.ConcurrentLinkedDeque` require O(n) time to compute the `size`. I will benchmark it as well. ------------- PR Comment: https://git.openjdk.org/jdk/pull/13383#issuecomment-1500996891
