RFR: 8316964: Security tools should not call System.exit [v6]

[Valerie Peng]

On Tue, 24 Oct 2023 16:37:12 GMT, Weijun Wang <weijun at openjdk.org> wrote:

>> Remove most `System.exit()` calls in various security tools and only leave one in the `main` method. This paves the way to convert them to JSR 199 tools.
>> 
>> Note: before this change, the behavior of a successful `main()` method execution is not consistent. Sometimes the method returns silently, sometimes a `System.exit(0)` is called somewhere. After this change, the method always returns silently. This makes sure that existing programs that calls the `main` method directly will continue and does not exit the VM.
>
> Weijun Wang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   simplify with pattern matching variable

Marked as reviewed by valeriep (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/15951#pullrequestreview-1695456281