Java regex help

Question

Can somebody please show me how to do a Java regex that takes in a string and returns a string with all characters removed BUT a-z and 0-9?

I.e. given a string a%4aj231*9.+ it will return a4aj2319

thanks.

Answer 1

\d is digit, \p{L} is a-z and A-Z.

str.replaceAll("[^\\d\\p{L}]", "");

Answer 2

If you want a-z and 0-9 but not A-Z then

str.replaceAll("[^\\p{Lower}\\p{Digit}]", "");

Answer 3

str = str.replaceAll("[^a-z0-9]+", "");

If you also meant to include uppercase characters, then you could use

str = str.replaceAll("[^A-Za-z0-9]+", "");

or the slightly leeter

str = str.replaceAll("[_\\W]+", "");