Question

Write a method in java named isValidEmail that takes a string as input parameter, and returns true if that string represents a valid email address, or false otherwise. An email address is considered valid if it follows this format “[email protected]”, where:

 user123 represents a sequence of word characters (i.e., letters, digits, or underscore) whose length is between 1 and 10 (inclusive), but the first character must be a letter

 domain represents a sequence of alphanumeric characters (i.e., letters or digits) whose length is between 1 and 12 (inclusive), but the first character must be a letter

 Exactly one character “@” separates the user name from the domain name

 ext is a sequence of lower case letters only whose length is between 1 and 3 (inclusive)

Examples: isValidEmail ("[email protected]") returns true isValidEmail ("[email protected]") returns false

Answer 1

/*******************************EmailValidation.java********************************/

public class EmailValidation {

   public static void main(String[] args) {

       System.out.println(isValidEmail("[email protected]"));
       System.out.println(isValidEmail("[email protected]"));
   }

   public static boolean isValidEmail(String email) {

       String username = email.split("@")[0];

       String namespace = email.split("@")[1];

       String domain = namespace.split("\\.")[0];

       String ext = namespace.split("\\.")[1];

       boolean validUsername = false; // true - no counter examples so far
       boolean validDomain = false;
       boolean validExt = false;
       for (int i = 0; i <= username.length() - 1; i++) {
           if (Character.isLetterOrDigit(username.charAt(i)) || username.charAt(i) == '_') {

               validUsername = true;
           }
       }
       for (int i = 0; i < domain.length() - 1; i++) {

           if (Character.isLetterOrDigit(domain.charAt(i)) && domain.length() <= 12) {

               validDomain = true;
           }
       }
       for (int i = 0; i < ext.length() - 1; i++) {

           if (Character.isAlphabetic(ext.charAt(0)) && ext.length() == 3) {

               validExt = true;
           }
       }
       if (email.contains("@") && email.contains(".")) {

           if (Character.isAlphabetic(username.charAt(0)) && username.length() <= 10 && validUsername && validDomain
                   && validExt) {

               return true;
           }

       }

       return false;
   }
}
/*******************output**********************/

true
false

Thanks a lot, Please let me know if you have any problem.............