code: public boolean isIndexed(String expression) {
      if (expression == null || expression.length() == 0) { return false; }
      for (int i = 0; i < expression.length(); i++) {
        char c = expression.charAt(i);
        if (c == Nested || c == MappedStart) {
          return false;
        } else if (c == IndexedStart) { return true; }
      }
      return false;
    }
docs: Indicate whether the expression is for an indexed property or not.
  
  @param expression The property expression
  @return <code>true</code> if the expresion is indexed,
  otherwise <code>false</code>