String (final String prefix) { // Manually do rule, since URIs can be null or empty if ((prefix == null) || (prefix.isEmpty())) { return null; } if (checkJDOMName(prefix) != null) { // will double-check null and empty names, but that's OK // since we have already checked them. return checkJDOMName(prefix); } // Cannot start with "xml" in any character case /* See Issue 126 - https://github.com/hunterhacker/jdom/issues/126 if (prefix.length() >= 3) { if (prefix.charAt(0) == 'x' || prefix.charAt(0) == 'X') { if (prefix.charAt(1) == 'm' || prefix.charAt(1) == 'M') { if (prefix.charAt(2) == 'l' || prefix.charAt(2) == 'L') { return "Namespace prefixes cannot begin with " + "\"xml\" in any combination of case"; } } } } */ // If we got here, everything is OK return null; }