[jdk20] RFR: 8297288: Example code in Scanner class

[Brian Burkhalter]

On Fri, 9 Dec 2022 18:32:37 GMT, Naoto Sato <naoto at openjdk.org> wrote:

> The example in `Scanner` directly uses `System.in` which may cause unwanted behavior when the default charset and the console charset differ. Using `Console.reader()` is more appropriate. Also changed examples into snippets.

Marked as reviewed by bpb (Reviewer).

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PR: https://git.openjdk.org/jdk20/pull/14