Regex to check if String is numeric or the word "all"

Question

I know how to check if a String is a positive double but how can I incorporate the function to check if the word is sell also?

This is what I use to check for positive double

sell2.matches("[+]?\\d*\\.?\\d+"))

EDIT: Answer in comment

Answer 1

private static final Pattern VALIDATOR = Pattern.compile("\\+?\\d+(\\.\\d+)?|all");
...
VALIDATOR.matcher(sell2).matches()

This is the regex you describe. Best have it compiled statically like this, otherwise calling sell2.matches(...) compiles it every time, and that's a performance hit.