* This file is part of the DiffX library.
* For licensing information please see the file license.txt included in the release.
* A copy of this licence can also be found at
This method will ensure that the mapping is actually unique, that is that the namespace URI correspond to one and only one prefix and that the prefix only corresponds to one and only one namespace URI.
uriThe namespace URI to map.
prefixThe prefix to use.
java.lang.NullPointerExceptionif the URI or prefix is
int count = 0;
actualPrefix = prefix + count++;