[PATCH] Inefficient ArrayList.subList().toArray() (original) (raw)
Martin Buchholz martinrb at google.com
Fri Jan 26 17:12:43 UTC 2018
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It may be that array-backed lists inheriting from AbstractList is not useful except when creating a prototype (or as a way of testing AbstractList!) because a high-quality implementation should always override.
On Fri, Jan 26, 2018 at 5:31 AM, Claes Redestad <claes.redestad at oracle.com> wrote:
On 2018-01-26 07:20, Martin Buchholz wrote:
It's still possible to find simple performance improvements in classes like ArrayList.
Indeed! It seems ArrayList.SubList delegates quite a few of its implementations to AbstractList and AbstractCollection, which uses iterators for things that could be done more efficiently with conventional for-loops. This includes contains, equals, hashCode, indexOf, lastIndexOf... I saw up to 7x improvements on some of these over the inherited implementations when providing specialized ones for ImmutableList.SubList as part of JDK-8193128 I'll file a bug and maybe even tinker with it when I find some time... /Claes
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