RFR: 8263552: Use String.valueOf() for char-to-String conversion in ObjectStreamClass

[Сергей Цыпанов]

On Mon, 1 Mar 2021 12:50:35 GMT, Andrey Turbanov <github.com+741251+turbanoff at openjdk.org> wrote:

> I think it's worth to cleanup other places with similar code too.

Done

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PR: https://git.openjdk.java.net/jdk/pull/2660