RFR: JDK-8274172: Convert JavadocTester to use NIO [v2]

[Pavel Rappo]

On Fri, 24 Sep 2021 12:57:02 GMT, Pavel Rappo <prappo at openjdk.org> wrote:

>> Jonathan Gibbons has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Address review comments;
>>   Move `JavadocTester.copyDir` to `ToolBox`; use FileVisitor code
>
> test/langtools/tools/lib/toolbox/ToolBox.java line 283:
> 
>> 281:                                 if (!Files.isDirectory(toSubdir))
>> 282:                                     throw e;
>> 283:                             }
> 
> If we do not expect the target directory to ever exist, we should remove this try-catch. This would make us fail fast, rather than add something to the existing file tree silently. Also, this situation could only happen in the first call to this method, right?
> Suggestion:
> 
>                             Files.copy(fromSubdir, toSubdir);

Let me clarify my sloppy writing.

> this situation could only happen in the first call to this method

Here I wanted to convey that if FileAlreadyExistsException is NOT thrown during the first call to preVisitDirectory, then this exception will NOT be thrown during subsequent calls to that same method, assuming we're exclusively modifying this tree. Indeed, if we are copying directory, then the first call to the visitor will be to this very method. If the target directory does not already exist, then neither do any subdirectories.

This FileVisitor example hints why there are no convenience methods for file tree copying: there are many ways to copy a file tree.

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PR: https://git.openjdk.java.net/jdk/pull/5644