[FIXED] Java requires slash instead of backslash on Windows in resources

Issue

I want to check if a file exists on resources and use this line:

getClass().getResource(resource.getResourceFullName()) != null

resource.getResourceFullName() is a method that returns just the file name without slashes like testevnvariables.yaml

I got that file did not exist. For your information, I use Windows and IntelliJ IDEA locally but prod is on Linux.

Then I tried to do this, but, again, the file does not exist:

getClass().getResource(File.separator + resource.getResourceFullName()) != null

and only when I added manually "/" I got "exists":

getClass().getResource("/" + resource.getResourceFullName()) != null

So my question is why it is happening? As far as I know, the default separator for Linux is slash, and for Windows is a backslash. File.separator returns a correct value for Windows - backslash but Java can't find it. I don't want to add "/" manually and want to be independent of the system and use something like System.lineSeparator() but for files. How can I do it?

I also tried to use File.exists() but with the same result.

And why when I found a file, Idea shows me this path (with slashes like on Linux):

.../target/test-classes/testevnvariables.yaml

Solution

A resource is something on the class path, which can be considered a sort of JVM specific virtual file-system (it is comprised of all JARs and directories, etc that have been specified on the class path). The file separator for this virtual file system is exclusively /. So, just use / and you are good to go. You don't need to fiddle with File.separator or anything, as the / is already system independent.

As an aside, even on Windows, most filesystem APIs allow you to use / and \ interchangeably.

Answered By - Mark Rotteveel
Answer Checked By - Cary Denson (JavaFixing Admin)