RFR: 8339704: Refactor StringConcatHelper simpleConcat [v6]

[Shaojin Wen]

On Sun, 8 Sep 2024 16:37:08 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> String concatenation is required in many places in java.lang. These static concat methods will be used instead of "+", so null value processing is added. This is also the motivation for using static concat methods instead of Concat1.
>
> I don't think replacing a lot of concatenations in java.base with `SCH.concat` is very appealing and needs to be motivated by a substantial performance advantage. And for the places where it's motivated we can make sure to sanitize and handle `null` arguments.

Yes, we shouldn't pay for things we don't need. I added null value handling to the parameters in SCF and removed it in SCH.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20726#discussion_r1751099693