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

[Claes Redestad]

On Mon, 30 Aug 2021 14:26:23 GMT, Сергей Цыпанов <github.com+10835776+stsypanov at openjdk.org> wrote:

>> No, I don't think so. The only use of this I can find is at line 1298 which effectively adds a substring: `putStringAt(dstOffset, (String) s, start, end);`
>
> What about lines 582, 1003 and 1175? E.g. 582
> 
> public AbstractStringBuilder append(String str) {
>     if (str == null) {
>         return appendNull();
>     }
>     int len = str.length();
>     ensureCapacityInternal(count + len);
>     putStringAt(count, str);             // couldn't it be putStringAt(count, str, 0, len);
>     count += len;
>     return this;
> }
> 
> Doing this here and in other places allows  to rid `private void putStringAt(int index, String str)` completely and reduce one nested method call, right?

I think you've got the wrong idea: We _want_ to use `putStringAt(int, String)` now since it can call into `String.getBytes(String, int, byte)`, which has a simpler and more efficient implementation than `String.getBytes(String, int, int, byte, int)`, since it avoids a couple of `<< coder` operations. This makes up for most of the improvement between my initial and the current version of this patch. 

(There's also no nested delegation from `putStringAt(int, String)` to `putStringAt(int, String, int, int)` in my proposed patch.)

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