Java Regex for alphanumeric characters

In this post, we will see how to create regex alphanumeric which will create only alphanumeric characters.
There are times when you need to validate the user’s input. It should contain only characters from a-z, A-Zor 0-9.
Here is simple regex for it.

Here is the explaination of above regex.

If you do not want to allow empty string, you can use + instead of *.

Java program to test regex alphanumeric characters.

package org.arpit.java2blog;

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

public class RegexExample {

    public static void main(String args[])
    {
        List<String> listOfUserNames=new ArrayList<>();
        listOfUserNames.add("Java2blog");
        listOfUserNames.add("Java-2-blog");
        listOfUserNames.add("Java2blog Tutorials");
        listOfUserNames.add("Java2blogTutorials");
        listOfUserNames.add("");

        String regex = "^[a-zA-Z0-9]*$";

        Pattern pattern = Pattern.compile(regex);

        for (String name : listOfUserNames)
        {
          Matcher matcher = pattern.matcher(name);
          System.out.println("Only Alphanumeric in "+name+" : "+ matcher.matches());
        }
    }
}

Output

That’s all about Java Regex – alphanumeric characters