[crac] RFR: Minor code cleanup and improvements

[Radim Vansa]

On Wed, 10 May 2023 15:21:57 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

>> Extracted non-essential changes from other PR.
>
> src/java.base/share/classes/javax/crac/CheckpointException.java line 50:
> 
>> 48:      * @param message the detail message.
>> 49:      */
>> 50:     public CheckpointException(String message) {
> 
> What if we remove this constructor and hide the other one? https://github.com/openjdk/crac/pull/60/files#r1190070472

First of all, I think that `javax.crac` should mirror `jdk.crac` API- and docs-wise. It will be much easier when everyone will be able to just change the imports.

About the constructor with message: I find a bit confusing when an exception is thrown because of some problem with `criu` but there's no actionable message. I have added a simple 'Native checkpoint failed' but we should probably point user to the dump4.log file. (`criuengine` should also make some sanity checks on permissions but that's another thing). I wouldn't object to hiding it, though.

About the one without: `Context` narrows the `throws` to CE/RE and since we expect users to implement Context this would give them no chance to throw checked exceptions, not even the aggregating one. Hiding that won't work.

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PR Review Comment: https://git.openjdk.org/crac/pull/64#discussion_r1190679470