RFR: 8357289: Break down the String constructor into smaller methods

[Chen Liang]

On Tue, 20 May 2025 01:21:34 GMT, Shaojin Wen <swen at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/String.java line 690:
>> 
>>> 688:                 .onUnmappableCharacter(CodingErrorAction.REPLACE);
>>> 689:         char[] ca = new char[en];
>>> 690:         int caLen = decodeWithDecoder(cd, ca, bytes, offset, length);
>> 
>> Let's restore the CharacterCodingException for now. I don't think we should change the exceptions as part of the break down.
>
> Restoring the exception handling here will cause the codeSize of the create method to be greater than 325. This exception will not occur here, so the exception handling is moved to decodeWithDecoder.

I think in this case, a better approach might be declaring `char[] ca` and `int cLen`/`caLen` -> the array decoder and the regular decoder can initialize these two variables, and share the final code that compress the strings.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25290#discussion_r2096694772