// the current folder is . but use whatever path you want. 
// paths can be a full, specific path like /Users/blah/Desktop
// on mac os x, or "C:\\blah\\somefolder" on windows
File folder = new File(".");  
String files[] = folder.list();
for (int i = 0; i < files.length; i++) {
  if (files[i].startsWith(".")) {  // skip hidden files, plus fake folders . and ..
    continue;
  }
  println(i + " " + files[i]);
}