Thread: Why is isDirectory true for File("c:")?

This is an interesting question. I'll try to expand on your question (questions should always come with an SSCCE whenever possible)...

Take this code for example:

import java.io.File;
 
public class Main{
 
	 public static void main(String[] args){
	        File f = new File("C:\\");
	        System.out.println("C:\\ is directory: " + f.isDirectory());
	        System.out.println("C:\\ exists: " + f.exists());
	        System.out.println("C:\\ absolute path: " + f.getAbsolutePath());
	        System.out.println();
 
	        f = new File("C:");
	        System.out.println("C: is directory: " + f.isDirectory());
	        System.out.println("C: exists: " + f.exists());
	        System.out.println("C: absolute path: " + f.getAbsolutePath());
	        System.out.println();
 
	        f = new File("X:");
	        System.out.println("X: is directory: " + f.isDirectory());
	        System.out.println("X: exists: " + f.exists());
	        System.out.println("X: absolute path: " + f.getAbsolutePath());
	        System.out.println();
	    }
 
}

(Note that I do have a C: drive, I do not have an X: drive)
This results in this output:

C:\ is directory: true
C:\ exists: true
C:\ absolute path: C:\

C: is directory: true
C: exists: true
C: absolute path: C:\Users\kworkman\Desktop\Tests

X: is directory: false
X: exists: false
X: absolute path: X:


So it seems to handle the C:\ correctly, but C: by itself results in strange output for a directory that doesn't actually exist. This is made stranger because it seems to handle the X: case correctly.

I'm not sure what's going on. I'll be curious to see what the smarter people come up with.

To come up with another case:
C:\ is directory: true
C:\ exists: true
C:\ absolute path: C:\

C: is directory: true
C: exists: true
C: absolute path: C:\

X: is directory: false
X: exists: false
X: absolute path: X:

JDK 7, win7 pro 64bit

Originally Posted by PhHein

JDK 7, win7 pro 64bit

Stranger still, that's exactly what I'm running, yet we get different output?

(I'm using Java 7 update 51)

I believe the culprit is this code from the WinNTFileSystem class:

public String resolve(File f) {
        String path = f.getPath();
        int pl = f.getPrefixLength();
        if ((pl == 2) && (path.charAt(0) == slash))
            return path;                        /* UNC */
        if (pl == 3)
            return path;                        /* Absolute local */
        if (pl == 0)
            return getUserPath() + slashify(path); /* Completely relative */
        if (pl == 1) {                          /* Drive-relative */
            String up = getUserPath();
            String ud = getDrive(up);
            if (ud != null) return ud + path;
            return up + path;                   /* User dir is a UNC path */
        }
        if (pl == 2) {                          /* Directory-relative */
            String up = getUserPath();
            String ud = getDrive(up);
            if ((ud != null) && path.startsWith(ud))
                return up + slashify(path.substring(2));
            char drive = path.charAt(0);
            String dir = getDriveDirectory(drive);
            String np;
            if (dir != null) {
                /* When resolving a directory-relative path that refers to a
                   drive other than the current drive, insist that the caller
                   have read permission on the result */
                String p = drive + (':' + dir + slashify(path.substring(2)));
                SecurityManager security = System.getSecurityManager();
                try {
                    if (security != null) security.checkRead(p);
                } catch (SecurityException x) {
                    /* Don't disclose the drive's directory in the exception */
                    throw new SecurityException("Cannot resolve path " + path);
                }
                return p;
            }
            return drive + ":" + slashify(path.substring(2)); /* fake it */
        }
        throw new InternalError("Unresolvable path: " + path);
    }

Both "C:" and "X:" have pl==2.
For "C:", this return statement is used:

if ((ud != null) && path.startsWith(ud))
                return up + slashify(path.substring(2));

For "X:", String dir = getDriveDirectory(drive); returns null, so the if statement is not entered, and the "fake it" return statement is used:

return drive + ":" + slashify(path.substring(2)); /* fake it */

java version "1.7.0_05"
Java(TM) SE Runtime Environment (build 1.7.0_05-b06)
Java HotSpot(TM) 64-Bit Server VM (build 23.1-b03, mixed mode)

On eclipse Indigo SR2

And I'm on eclipse Juno SR1

This doesn't guarantee this is what eclipse is using, but in my case, they are the same:

C:\Users\kworkman>java -version
java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)

I think Aussie is on the right track, but I'm still not sure why we get different output.

Maybe your FileSystem objects are different. I'm not sure how you can get the instance of that. It seems to be protected.