RFR: 8186958: Need method to create pre-sized HashMap [v12]

[XenoAmess]

On Sat, 9 Apr 2022 04:33:00 GMT, liach <duke at openjdk.java.net> wrote:

> Quick question: If the maps are intended to be fixed-size, can't the users just call `new HashMap<>(size, 1)`, increasing the growth factor to prevent growth?

@liach this questions equals question : "why default load factor be 0.75 not 1"
In short, when larger the load factor, smaller memory use, and larger hash-collide rate, larger crud time cost.
when smaller the load factor, larger memory use, and smaller hash-collide rate, smaller crud time cost.
As for why default load factor be 0.75 but not 1, it is historical to me. it is already 0.75 when I first learn java and never changed then. But I guess there be some empirical formula behind it.

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PR: https://git.openjdk.java.net/jdk/pull/7928