CODEWITHSUNDEEP
javalinuxnio
ben3000
ben3000

Reputation: 4989

Path.startsWith returns false for a Windows file path on Linux

Why would this be?

Path parent1 = Paths.get("/flugel/borf/noggin");
Path child1 = Paths.get("/flugel/borf/noggin/foo/bar/baz.jpg");
System.out.println("child1 startsWith parent1? " + child1.startsWith(parent1));
System.out.println(child1.getFileSystem());
System.out.println(parent1.getFileSystem());

Path parent2 = Paths.get("C:\\foo");
Path child2 = Paths.get("C:\\foo\\bar\\baz.jpg");
System.out.println("child2 startsWith parent2? " + child2.startsWith(parent2));
System.out.println(child2.getFileSystem());
System.out.println(parent2.getFileSystem());

returns

child1 startsWith parent1? true
sun.nio.fs.LinuxFileSystem@f5f2bb7
sun.nio.fs.LinuxFileSystem@f5f2bb7
child2 startsWith parent2? false
sun.nio.fs.LinuxFileSystem@f5f2bb7
sun.nio.fs.LinuxFileSystem@f5f2bb7

I'm running Java 8 on Ubuntu, but nothing about the javadocs for Path.startsWith explains why this occurs. Neither file path contains any actual files.

Upvotes: 5

Views: 1650

Answers (3)

Pooya
Pooya

Reputation: 6126

As described in the Javadocs, Java uses the "path separator" to determines the current operating environment path separator character. This can be accessed via:

System.getProperty("path.separator");

on UNIX based system it is "/", while on Windows systems it is "\". If you want to change these properties you can use the following to achieve that:

Properties p = System.getProperties();
p.put("path.separator", "\\");
System.setProperties(p);

Upvotes: 0

user987339
user987339

Reputation: 10707

You have to check the code to see what is actually going on. So when you create a Path normalizeAndCheck function is called. In your case this is called on sun.nio.fs.UnixPath. Since path delimiter for *nix is / path strings will be normalized by /.

In case of Windows paths there are no / so they will stay exactly the same, so it will compare "C:\\foo" "C:\\foo\\bar\\baz.jpg" which are different strings and hence no common prefix.

Upvotes: 2

Sanjeev
Sanjeev

Reputation: 9946

I think below line from Java Docs of java.nio.file.Path answers your question

An object that may be used to locate a file in a file system. It will typically represent a system dependent file path.

Upvotes: 1

Related Questions