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I do not own a Windows copy, but would like to know the behavior and recommended usage in Java for representing a path such as \autoexec.bat under Windows?

Semantically, such a path would represent the file autoexec.bat on the root of any file system. Thus it would need to be resolved against a path representing a disk drive (such as C:\) before representing a file. In that sense, it is not absolute. However, it also does not have a root component, I suppose.

Can such path be created when running the JVM on Windows? If so, what would getRoot() and isAbsolute() return?

I tried the following code using Memory File System, but this throws InvalidPathException: “path must not start with separator at index 1: \truc”. Does this faithfully reflect the behavior under Windows, or is it a quirk of this specific library?

try (FileSystem fs = MemoryFileSystemBuilder.newWindows().build()) {
    final Path truc = fs.getPath("\\truc");
    LOGGER.info("Root: {}.", truc.getRoot());
    LOGGER.info("Abs: {}.", truc.isAbsolute());
    LOGGER.info("Abs: {}.", truc.toAbsolutePath());
}

Such paths are valid in the Windows terminal, or at least they were last time I used Windows (a long time ago). It would be handy to create such path in order to mark that the path is “absolute” (in the sense of starting with a backslash, thus not relative to a folder), but still leave the path without a driver letter specified. Then such a path can be (later) resolved to C:\autoexec.bat or D:\autoexec.bat or …

Olivier Cailloux
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1 Answers1

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In Windows, \\ refers to the current drive which is C:\ in my case.

Not sure how the MemoryFileSystemBuilder works but the following code 

File file = new File("\\test.txt");
final Path truc = file.toPath();
System.out.println("Root: " + truc.getRoot().toString());
System.out.println("Abs: " + truc.isAbsolute());
System.out.println("Abs: " + truc.toAbsolutePath().toString());

gives the below output

Root: \
Abs: false
Abs: C:\test.txt
Eeshwar Ankathi
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    *"In Windows, `\\ ` refers to the base system drive which is `C:\ ` in my case."* - This is incorrect. A filename starting with a single backslash designates an [absolute path](https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file#fully-qualified-vs-relative-paths) on the **current volume**. This may or may not be the volume designated by `C:`. The volume may not even have a drive letter assigned. The system volume need not have the `C` drive letter assigned either. – IInspectable Aug 05 '19 at 09:06
  • You mean \, not \\, I suppose. – Olivier Cailloux Aug 05 '19 at 11:51
  • @OlivierCailloux In java, \ should be escaped. So, we use \\ – Eeshwar Ankathi Aug 05 '19 at 11:53
  • I understand, but your first sentence reads as if you were talking about the path consisting of _two_ backslashes in Windows. You mean one, there. (Admittedly, I am nitpicking, but some readers might get confused perhaps.) – Olivier Cailloux Aug 05 '19 at 11:55