The following sample code demostrates the problem of Path.toUri(). It encodes umlaut incorrectly as 117,776.

import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
public class Test {
    public static void main(String[] args) throws MalformedURLException, IOException {
        final File f = new File ("Frühling").getCanonicalFile(); //NOI18N
        f.mkdir();
        final String io = f.toURI().toURL().toString();
        final String nio = f.toPath().toUri().toURL().toString();
        final boolean res = io.equals(nio);
        System.out.println(res);
        System.out.println(io);
        System.out.println(nio);
    }
}

On Ubuntu with JDK 8 the same problem as on Mac, seems a problem in UNIX implementation of NIO FileSystem.

Related NetBeans bug:
https://netbeans.org/bugzilla/show_bug.cgi?id=246438