RFR: 8186958: Need method to create pre-sized HashMap [v7]

[XenoAmess]

> 8186958: Need method to create pre-sized HashMap

XenoAmess has updated the pull request incrementally with two additional commits since the last revision:

 - update jmh
 - refine javadoc; refine implement when expectedSize < 0

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7928/files
  - new: https://git.openjdk.java.net/jdk/pull/7928/files/5b7eec6c..293b949c

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7928&range=06
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7928&range=05-06

  Stats: 32 lines in 2 files changed: 27 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7928.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7928/head:pull/7928

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