RFR: 8273100: Improve AbstractStringBuilder.append(String) when using CompactStrings [v3]

[Claes Redestad]

On Mon, 30 Aug 2021 13:35:23 GMT, Сергей Цыпанов <github.com+10835776+stsypanov at openjdk.org> wrote:

>> Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Simplify and call getBytes(String, int, byte) when possible
>
> src/java.base/share/classes/java/lang/AbstractStringBuilder.java line 1714:
> 
>> 1712: 
>> 1713:     private void inflateIfNeededFor(String input) {
>> 1714:         if (COMPACT_STRINGS && (coder != input.coder())) {
> 
> I'm not completely sure whether it's a good idea in terms of maintainability, but I think this can be simplified a bit more. Currently in both `String` and `ASB` we have implementations of `coder()` very much alike:
> 
> // ASB
> final byte getCoder() {
>     return COMPACT_STRINGS ? coder : UTF16;
> }
> 
> //String
> byte getCoder() {
>     return COMPACT_STRINGS ? coder : UTF16;
> }
> 
> Here we have this condition
> 
> if (COMPACT_STRINGS && (coder != input.getCoder())) {}
> 
> where the right operand of `&&` is evaluated only when `COMPACT_STRINGS` is `true` and hence it always returns the value of `coder` field. This means we can reference it directly as
> 
> if (COMPACT_STRINGS && (coder != input.coder)) {}

I'm not sure if this'd give us enough to motivate the refactor, especially since we'd have to widen the visibility of `String.coder`. Maybe startup could be helped a little. Either way it feels out of scope for this change, don't you think?

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PR: https://git.openjdk.java.net/jdk/pull/5291