Question

I need a method that can tell me if a String has non alphanumeric characters.

For example if the String is “abcdef?” or “abcdefà”, the method must return true.

Answer 1

Using Apache Commons Lang:

!StringUtils.isAlphanumeric(String)

Alternativly iterate over String’s characters and check with:

!Character.isLetterOrDigit(char)

You’ve still one problem left:
Your example string “abcdefà” is alphanumeric, since à is a letter. But I think you want it to be considered non-alphanumeric, right?!

So you may want to use regular expression instead:

String s = "abcdefà";
Pattern p = Pattern.compile("[^a-zA-Z0-9]");
boolean hasSpecialChar = p.matcher(s).find();