RFR: 8274163: Use String.equals instead of String.compareTo in jdk.jcmd

[Alex Menkov]

On Wed, 22 Sep 2021 19:14:03 GMT, Andrey Turbanov <github.com+741251+turbanoff at openjdk.org> wrote:

> In several places, String.compareTo was _compared_ with 0 ( via `== 0` or `!= 0`).
> Instead of this, we can use String.equals calls. `String.equals` is faster and shorter.

Marked as reviewed by amenkov (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/5637