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

[Tagir F.Valeev]

On Tue, 25 May 2021 10:31:33 GMT, Patrick Concannon <pconcannon at openjdk.org> wrote:

>> Tagir F. Valeev has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Indent some lines to make GitHub diff happier
>
> src/java.base/share/classes/java/util/GregorianCalendar.java line 1730:
> 
>> 1728:         int value = -1;
>> 1729:         switch (field) {
>> 1730:             case MONTH -> {
> 
> HI @amaembo, thanks for taking a look at this.
> 
> I think you should be careful here, and ask is introducing the enchanced switch adding any value? While I think the enchanced switch can be valuable when it makes the code more readable, it shouldn't be introduced just for the sake of using it.

@pconcannon thank you for review!

In this particular place, it makes the code more better in the following points:
- It removes `break;` operators at the end of each branch, which add nothing but a visual noise
- It makes the whole switch shorter by 22 lines
- Using `->` syntax clearly states that no branch in this switch has a fall-through behavior, so the code reader should not check every branch to ensure this. Just see very first `->` and you already know that no fallthrough is here.
- In case if new branches will appear in the future, the new-style switch will protect future maintainers from accidental fall-through, an error that often happens with old-style switches.

> src/java.base/share/classes/java/util/PropertyPermission.java line 337:
> 
>> 335:      */
>> 336:     static String getActions(int mask) {
>> 337:         return switch (mask & (READ | WRITE)) {
> 
> Just a suggestion, but it might be more readable if you align the lambda operators

Thank you for pointing to this. Actually, I just noticed that there was some kind of vertical alignment before my change. I added vertical alignment for single-line switch rules.

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