Compare a Path element to a string

[Weijun Wang]

Hi Alan

I'm profiling the new FilePermission implementation and found a lot of 
time spending on comparing a Path to a string, and the path has only one 
element.

Here are them:

1. Comparing with "-":

   Path lastName = npath.getFileName();
   if (lastName != null && lastName.toString().equals("-")) { ... }

2. Comparing with "":

   p = p2.relativize(p1).normalize();
   if (p.getName(0).toString().isEmpty()) { ... }

3. Comparing with "..":

   for (Path item: p) {
      String s = item.toString();
      if (!s.equals("..")) { ... }
   }

I can think of comparing with static final Path fields, but is there a 
even faster way?

Thanks
Max