RFR: 8199594: Add doc describing how (?x) ignores spaces in character classes

[Pavel Rappo]

On Mon, 28 Jun 2021 20:50:42 GMT, Ian Graves <igraves at openjdk.org> wrote:

> 8199594: Add doc describing how (?x) ignores spaces in character classes

src/java.base/share/classes/java/util/regex/Pattern.java line 833:

> 831:      * <p> Comments mode can also be enabled via the embedded flag
> 832:      * expression {@code (?x)}.
> 833:      *

Nit: is this extra line necessary?

-------------

PR: https://git.openjdk.java.net/jdk/pull/4618