Problem is matches("^([A-Z]):"))
since String#matches
matched full input not just a part of it.
Try this instead to make it match full line:
if (!arcvalFileFormBean.getTxtFileReview().matches("((?i)(?s)[A-Z]):.*")) {
PS: ^
and $
anchors are also not required in String#matches
since that is implicit.
(?i)
=> Ignore case(?s)
=> DOTALL (mase DOT match new lines as well)