firstname1 = firstname1.replaceAll("[0-9]","");
Extract numbers from a string
Character.isDigit(str.charAt(i))
Character.isLetter(str.charAt(i))
Character.isAlphabetic(str.charAt(i))
String password = "cnE4g1Z5y9A";
String[] letters= password.split("[0-9]"); ==> cnEgZyA
String[] letters= password.split("[A-Za-z]"); ==> 4159