Hi Peter,
You are correct. Thanks. I'll remove that initial value of 16.
Naoto
On 5/5/20 9:37 AM, Peter Levart wrote:
Hi Naoto,
On 4/30/20 12:18 AM, naoto.s...@oracle.com wrote:
Hello,
Please review this small fix to the following issue:
https://bugs.openjdk.java.net/browse/JDK-8244152
The proposed changeset is located at:
https://cr.openjdk.java.net/~naoto/8244152/webrev.00/
The hash map used there didn't have initial capacity, even though the
exact numbers are known.
Well, it has to be calculated 1st (countTokens), but I guess this pays
off when HashSet (the backing HashMap) does not have to be rehashed then.
The expression you use:
Math.max((int)(tokens.countTokens() / 0.75f) + 1, 16)
...has a minimum value of 16. Why is that? 16 is just HashMap's default
initialCapacity if not specified explicitly. But if you only want to
store say 1 entry in the map, you can specify 2 as initialCapacity and
HashMap will happily work for such case without resizing.
So you could just use:
(int)(tokens.countTokens() / 0.75f) + 1
And even this expression is sometimes overshooting the minimal required
value by 1 (when # of tokens is "exact" multiple of 0.75f, say 6). I
think the following could be used to optimally pre-size the HashMap with
default load factor 0.75:
(tokens.countTokens() * 4 + 2) / 3
Regards, Peter
Naoto
