Question

I am trying to find a particular pattern in my strings and my knowledge of regex is quite basic. To find lower case letters I can use [a-z0-9]+ but how would I go about finding the preceding and proceding characters?

Allowed examples:
(A), AB, ABC, [ABC], .AB' , @ABCD#. In essence only uppercase characters(any length), or uppercase(any length) with preceding or proceding or both(front and back), special chars.
Not Allowed:
abABCaa , ABCaa , aaAB , 123ABC , 12ABGGabc , aaBaa etc. In essence uppercase letters(any length) with preceding or proceding or both, alphabets or numbers.

How can I write a regex that filters either the allowed examples or the not allowed examples?
Hope I am clear

Answer 1

This will match 3 groups: the Matched uppercase, the characters preceding it and the characters after it. If groups are not desired, just remove the parenthesis.

([^a-z0-9]*)([A-Z]+)([^a-z0-9]*)

For more information about matching and grouping please refer to the proper Javadoc .
Also, a suggestion for testing regex online