FileFilter for executable files

Question

I'm trying to make a FileFilter that only accepts executable files and directories. My attempt is shown below:
    public boolean accept(File f)
        if(f.isDirectory())
            return true;
        SecurityManager sm = new SecurityManager();
        try
            System.out.println(f.getPath());
            sm.checkExec(f.getPath());
        } catch (SecurityException e) {
            return false;
        return true;
    }This isn't returning anything but directories. It also strikes me as odd that the SecurityManager works by throwing exceptions, when it isn't really exceptional to have a file not be executable.
Any help here would be appreciated.

Answer 1

I wanted something that would work on any system. I figured that this functionality should exist simply because it is useful. As for the argument that it is too OS specific, I disagree. Every developed OS has some means for determining if a file is an executable program. Just as the Graphics package is supported on multiple systems despite different implementations, I believe that filetype identification could be done in the JREs.
But it looks like it isn't done. That appears to be the answer to my question.