columnUsername = columnUsername.replace("Domain\\", "");
Try this?
The reason I am asking is because in java replace and replaceAll methods handle the searchFor
string differently. While replace method treats it as a character squence, replaceAll treats it as regex. This is an age old issue with Java and while using replaceAll method you will have to use \\\\
to escape a single \
as internally these are compiled by Java and then by regex. If you use replace then it is just compiled by Java and \\
will be treated a \