How to determine if a String has non-alphanumeric characters?

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(); 

Answer 2

One approach is to do that using the String class itself. Let's say that your string is something like that:

String s = "some text"; boolean hasNonAlpha = s.matches("^.*[^a-zA-Z0-9 ].*$"); 

one other is to use an external library, such as Apache commons:

String s = "some text"; boolean hasNonAlpha = !StringUtils.isAlphanumeric(s);