How to check if only chosen characters are in a string?

Question

What\'s the best and easiest way to check if a string only contains the following characters:

abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_         


        

Answer 1

if (string.matches("^[a-zA-Z0-9_]+$")) {
  // contains only listed chars
} else {
  // contains other chars
}