RFR: CODETOOLS-7903091: Convert jtreg to use NIO

[Jonathan Gibbons]

On Tue, 8 Feb 2022 07:15:11 GMT, Iris Clark <iris at openjdk.org> wrote:

>> Please review a medium-big, conceptually simple but occasionally tricky update to jtreg, to use `java.nio.file.Path` instead of `java.io.File` where reasonable.
>> 
>> While most of the changes are formulaic and follow the obvious patterns, there were some noteworthy points:
>> 
>> * The most complicated class to change was `Locations`, which does the most work to derive new paths. In particular, the semantics of `new File(a, b)` do not always match `Path.of(a).resolve(b)` for corner cases like when `a` is`null` or empty, or when `b` is absolute.
>> 
>> * The NIO equivalent for some operations on `File` throw checked IO exceptions.  These methods were wrapped to to throw a custom unchecked IO exception.
>> 
>> * The NIO equivalent for creating a new file (`Path`) throws an unchecked `InvalidPathException` exception. The use sites are too numerous to handle individually.  The solution is to catch exceptions like these (and the ones described in the previous bullet) at strategic points where they can be handled or wrapped back into (existing) checked exceptions.
>> 
>> The development has been iterative, frequently running the jtreg internal tests locally (on a Mac) and occasionally building on a CI system (Linux).  We should do more exhaustive testing with JDK before this work ever gets promoted.
>
> src/share/classes/com/sun/javatest/regtest/util/FileUtils.java line 99:
> 
>> 97:      * @return {@code -1}, {@code 0} or {@code 1} according to whether the last modified time of the first file
>> 98:      *          is less than, equal to, or greater than the last modified time of the second file
>> 99:      *
> 
> Not sure I understand the spacing convention, but the presence of this empty line and those at lines 109, 111, 113, and 128 may be inconsistent.

Inconsistency is bad, especially within a new file. I was aiming for a more spaced-out look, more similar to the core-libs style, with blank lines between groups of tags.

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PR: https://git.openjdk.java.net/jtreg/pull/50