Check out example codes for "java string length validation regex". It will help you in understanding the concepts better.

Code Example 1

//Password validation example
public static Boolean validPassword(String password) throws IllegalArgumentException {
   if (!password.matches("\\w{6,}"))/*Or '(password.matches("\\w{6,}") == false)'*/ {
      throw new IllegalArgumentException("Password must be at least 6 characters long.");
   //'("\\w{int}")' => Must be int characters long.
   //'("\\w{int,}")' => Must be AT LEAST int characters long and can be longer.
   //'("\\w{int1,int2}")' => Must be BETWEEN int1 AND int2 characters long.
   return true;

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