Java Paths.get() strange behavior on Linux

Question

I am currently writing some code in which I work with files a lot. I implemented all file paths processing (concatenation, normalization, etc) using the Java 7 nio classes Paths and Path. On Windows everything works as expected however on Linux the Paths class behavior seems to be broken.

For example the following code:

    System.out.println(File.separator);
    System.out.println(FileSystems.getDefault());
    Path path = Paths.get("../dir1/", "\\dir2\\file1").toAbsolutePath().normalize();
    System.out.println(path);
    if(path.toFile().exists()) {
        System.out.println(path + " exists");
    }

on Windows prints the following output:

\
sun.nio.fs.WindowsFileSystem
D:\projects\dir1\dir2\file1
true

but the same code on Linux Ubuntu 14.04 on both Java 1.7.0_79 (64 bit) and Java 1.8.0_60 (64 bit) leaves the path un-normalized:

/
sun.nio.fs.LinuxFileSystem
/home/semi/dir1/\dir2\file1

Also even if the file is at path /home/semi/dir1/dir2/file1 exists it is reported as non-existent by path.toFile().exists().

I looked a bit over LinuxFileSystem.java and WindowsFileSystem.java and it seems that on windows the path is checked for both / and \ characters (in WindowsPathParser.isSlash(char c) method). Shouldn't the Linux implementation do the same?

Is this a bug in sun.nio.fs.LinuxFileSystem implementation or am I doing something wrong?

Also do you know any alternative to make sure Linux paths are parsed and normalized correctly (without doing all the parsing manually).

Answer 1

In Windows, / is not a valid character in a filename so any code can assume it's a wrongly typed path separator.

In Linux, just about any byte is acceptable in a filename. In your Paths.get(), you're effectively joining a path called dir1 (1 level deep) and a path called \dir2\file1 (also 1 level deep).