RFR: JDK-8306112 Implementation of JEP 445: Flexible Main Methods and Anonymous Main Classes (Preview) [v2]

[Jim Laskey]

> Add flexible main methods and anonymous main classes to the Java language.

Jim Laskey has updated the pull request incrementally with one additional commit since the last revision:

  PreviewFeatures.isEnabled()

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13689/files
  - new: https://git.openjdk.org/jdk/pull/13689/files/cfe08f33..a55af76c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13689&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13689&range=00-01

  Stats: 32 lines in 3 files changed: 2 ins; 27 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/13689.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13689/head:pull/13689

PR: https://git.openjdk.org/jdk/pull/13689