RFR: 8267587: Update java.util to use enhanced switch [v3]

[Tagir F.Valeev]

On Tue, 25 May 2021 03:48:41 GMT, Tagir F. Valeev <tvaleev at openjdk.org> wrote:

>> src/java.base/share/classes/java/util/regex/CharPredicates.java line 217:
>> 
>>> 215:             case "WORD" -> WORD();
>>> 216:             default -> null;
>>> 217:         };
>> 
>> This file has lots of changes which are difficult to review. Maybe it should be split out of this PR.
>
> *sigh* GitHub diff tool is really poor and outdated. Here's how it looks in IntelliJ IDEA diff view:
> ![image](https://user-images.githubusercontent.com/5114450/119436474-6b455b80-bd46-11eb-8865-8b7f30826a8d.png)

I played with indentations and found a way to make GitHub diff happier. Now, lines like `? UPPERCASE().union(LOWERCASE(), TITLECASE())` are probably a little bit too far to the right but it's still acceptable and diff looks much easier to review now.

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PR: https://git.openjdk.java.net/jdk/pull/4161