How to check if a string is of a specific pattern [closed]

Answer 1

You should have a closer look at regular expressions. A tutorial is e.g. here at regular-expressions.info.

An example for your Pattern could be

^[A-Z]{2}\d{4}$

you can see it here on Regexr.com a good place to test regular expressions online.

Here is java regex tutorial there you can see how you call them in Java.