regular expression java password

Question

Hey I have searched through stackoverflow and can't seem to find an answer. I need to check if the typed password only contains letters and numbers.

here's the code

System.out.println("Type the Password for the new user: ");
    String password = input.nextLine();

    if (!password.matches("[^A-Za-z0-9]")) {            
         System.out.println("The password must only contain letters and/or numbers");
            showAddUser();
    }else{

             System.out.println("The password is valid");

What am I doing wrong ? Help appreciated :)

Answer 1

Try this:

if (!password.matches("^([A-Za-z0-9]+)$")) {   

What a shame - this regular expression excludes "correct horse battery staple".

http://xkcd.com/936/

Answer 2

With String.matches("[A-Za-z0-9]") you're actually matching whether the String contains of exactly one alphanumeric. You probably want it to be repeated. You could try String.matches("[A-Za-z0-9]+") to match at least one alphanumeric, not exactly one.

By the way, I wouldn't trust a system which doesn't allow me to use punctuation as well.

Answer 3

删除否定项：

if (password.matches("[^A-Za-z0-9]")) { 

Answer 4

Just as an alternative approach: you can use StringUtils.isAlphanumeric(String str)

https://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/StringUtils.html#isAlphanumeric%28java.lang.String%29

Answer 5

尝试if (!password.matches("[^A-Za-z0-9]+"))

Answer 6

You can use VT password library for password validation. You can use AllowedCharacterRule or RegexRule for this. With this tool you can easily add more rules if needed later.