[PATCH] Inefficient ArrayList.subList().toArray() (original) (raw)

Claes Redestad claes.redestad at oracle.com
Fri Jan 26 13:31:31 UTC 2018


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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