How to test a string if it has the right format?

[Java checker (Gast)]

Hello,
I have a string which a user should input into my program. And I wanna 
check if the string always has the correct format. What is the best way 
to check this Format in java ?

[One digit 0-9];[Hex code like 0x21DE40AF];[Digit 0-99];[One Digit 0-9]

Thanks

[gdfgdfgdg (Gast)]

standard Clib

regexec
regcomp

[gdfgdfgdg (Gast)]

sorry ^^ don't see "java" ...

but search for "regex" - regular expression

[quotendepp (Gast)]

if i'm not completely wrong there's something like String.match(pattern) 
which uses regex. and regex absolutely suitable for this task