RFR 8005698 : Handle Frequent HashMap Collisions with Balanced Trees (original) (raw)

Brent Christian brent.christian at oracle.com
Fri May 31 18:27:35 UTC 2013

On 5/31/13 7:10 AM, Alan Bateman wrote:

I've read through the latest webrev, overall very good work.

I had to read splitTreeBin a few times to convince myself as to how the keys re-hash. I wonder if would be helpful to beef up the comment on this method.

I think that's a good idea:

--- 342,355 ---- int loCount = 0, hiCount = 0; TreeNode<K,V> e = oldTree.first; TreeNode<K,V> next; ! ! // This method is called when the table has just increased capacity, ! // so indexFor() is now taking one additional bit of hash into ! // account ("bit"). Entries in this TreeBin now belong in one of ! // two bins, "i" or "i+bit", depending on if the new top bit of the ! // hash is set. The trees for the two bins are loTree and hiTree. ! // If either tree ends up containing fewer than TREE_THRESHOLD ! // entries, it is converted back to a linked list. while (e != null) {

Otherwise I didn't see anything obviously wrong. Minor alignment issue with the comments on Holder.

Fixed, thanks.

-Brent

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