docs: public static boolean isFullyQualifiedClassname( String classname ) {
          if (classname == null) return false;
          String[] parts = classname.split("[\\.]");
          if (parts.length == 0) return false;
          for (String part : parts) {
              CharacterIterator iter = new StringCharacterIterator(part);
              // Check first character (there should at least be one character for each part) ...
              char c = iter.first();
              if (c == CharacterIterator.DONE) return false;
              if (!Character.isJavaIdentifierStart(c) && !Character.isIdentifierIgnorable(c)) return false;
              c = iter.next();
              // Check the remaining characters, if there are any ...
              while (c != CharacterIterator.DONE) {
                  if (!Character.isJavaIdentifierPart(c) && !Character.isIdentifierIgnorable(c)) return false;
                  c = iter.next();
              }
          }
          return true;
      }