RFR: 8356420: Provide examples on wrapping System.in [v2]

[Naoto Sato]

> With the introduction of `stdin.encoding` ([JDK-8350703](https://bugs.openjdk.org/browse/JDK-8350703)), some guidance for users to decode `System.in` would be desirable. Adding examples in the field description would help.

Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:

  Reflects a review comment

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25155/files
  - new: https://git.openjdk.org/jdk/pull/25155/files/844aa0a7..496dd39d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25155&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25155&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25155.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25155/head:pull/25155

PR: https://git.openjdk.org/jdk/pull/25155