code: @Override
      public final String getNamespaceURI(String prefix)
      {
          if (prefix == null) {
              throw new IllegalArgumentException(ErrorConsts.ERR_NULL_ARG);
          }
          if (prefix.length() == 0) {
              if (mDepth == 0) { // unexpected... but let's not err at this point
                  /* 07-Sep-2007, TSa: Default/"no namespace" does map to
                   *    "URI" of empty String.
                   */
                  return XmlConsts.DEFAULT_NAMESPACE_URI;
              }
              return mCurrElement.mDefaultNsURI;
          }
          if (prefix.equals(XMLConstants.XML_NS_PREFIX)) {
              return XMLConstants.XML_NS_URI;
          }
          if (prefix.equals(XMLConstants.XMLNS_ATTRIBUTE)) {
              return XMLConstants.XMLNS_ATTRIBUTE_NS_URI;
          }
          /* Ok, need to find the match, if any; starting from end of the
           * list of active namespaces. Note that we can not count on prefix
           * being interned/canonicalized.
           */
          return mNamespaces.findLastNonInterned(prefix);
      }
docs: /*
  /////////////////////////////////////////////////////////
  Implementation of NamespaceContext:
  /////////////////////////////////////////////////////////