Regular Expression for String representing DNA code

Question

Hello I am trying to use regular expressions in a java program. I would like the regex to identify a String of unknown length and whose charachters are only \'C\', \'A\', \'G\'

Answer 1

Easy, just use a character class:

[CAGT]+

Or if the entire string has to comprise of the chars CAGT for it to match:

^[CAGT]+$