RFR: 8340710: Optimize DirectClassBuilder::build

[Chen Liang]

On Mon, 23 Sep 2024 00:20:09 GMT, Shaojin Wen <swen at openjdk.org> wrote:

>> For clarity, I think using Integer.toUnsignedLong on the shift result is better
>
> If minorVersion > 0xFFFF, the result of using Integer.toUnsignedLong will be wrong. I guess this is the reason why the previous version build failed

Should we add a `& 0xFFFF` on `majorVersion` to defend against `majorVersion > 0xFFFF` too?

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PR Review Comment: https://git.openjdk.org/jdk/pull/21118#discussion_r1772318887