Check if string contains only non-alphanumeric characters

Question

I need to check strings to see if they only contain "Nonalphanumeric characters". basically I can have a string that is ",,.hi" and this would be okay. because it contains alphanumeric characters as well as non alphanumeric, but a line that is just "@@#!" this would be deleted. It seems like I would need some type of "Contains" that's not the normal java contains.

Here is what I have tried.

if(line.matches("[^a-zA-Z\\d\\s:]")){
   line = line;
} else {
   line = line.replace(line, "");
}

Answer 1

If you just want to see if it contains an alphanumeric, then you can find() it

import java.util.regex.Matcher;
import java.util.regex.Pattern;


    public String clean(String line) {
        Pattern p = Pattern.compile("\w"); 

        Matcher m = p.matcher(line);
        if (m.find()) {
          return line; // found any character or digit, keep the line
        }
        return ""; // else return nothing
    }

Answer 2

Use this regex:

if(!line.matches("^[a-zA-Z0-9!]*$"))

to check if there is any non-alphanumeric character in your string line :