How to only match a single instance of a character?

Question

Not quite sure how to go about this, but basically what I want to do is match a character, say a for example. In this case all of the following would not contain ma

Answer 1

You may use a combination of a lookbehind and a lookahead:

(?

See the regex demo and the regex graph:

Details

• (? - a negative lookbehind that fails the match if, immediately to the left of the current location, there is a a char
• a - an a char
• (?!a) - a negative lookahead that fails the match if, immediately to the right of the current location, there is a a char.