code: private static Attr findMatchingAttr(final List<Attr> attrs,
                                           final Attr attrToMatch) {
          final boolean hasNs = attrToMatch.getNamespaceURI() != null;
          final String nsToMatch = attrToMatch.getNamespaceURI();
          final String nameToMatch = hasNs ? attrToMatch.getLocalName()
              : attrToMatch.getName();
          for (Attr a : attrs) {
              if (((!hasNs && a.getNamespaceURI() == null)
                   ||
                   (hasNs && nsToMatch.equals(a.getNamespaceURI())))
                  &&
                  ((hasNs && nameToMatch.equals(a.getLocalName()))
                   ||
                   (!hasNs && nameToMatch.equals(a.getName())))
                  ) {
                  return a;
              }
          }
          return null;
      }
docs: Find the attribute with the same namespace and local name as a
  given attribute in a list of attributes.