RFR: 8356420: Provide examples on wrapping System.in [v4]

[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 more comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25155/files
  - new: https://git.openjdk.org/jdk/pull/25155/files/6f8101cf..9621320c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25155&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25155&range=02-03

  Stats: 16 lines in 3 files changed: 8 ins; 2 del; 6 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