RFR: 8284780: Need methods to create pre-sized HashSet and LinkedHashSet

[XenoAmess]

as title.

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Commit messages:
 - 8284780: Need methods to create pre-sized HashSet and LinkedHashSet

Changes: https://git.openjdk.java.net/jdk/pull/8302/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8302&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284780
  Stats: 34 lines in 2 files changed: 34 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8302.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8302/head:pull/8302

PR: https://git.openjdk.java.net/jdk/pull/8302