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

My turn:

static final Pattern bad = Pattern.compile("\\W|^$");
//...
if (bad.matcher(suspect).find()) {
  // String contains other characters
} else {
  // string contains only those letters
}

Above searches for single not matching or empty string.

And according to JavaDoc for Pattern:

\w  A word character: [a-zA-Z_0-9]
\W  A non-word character: [^\w]