Java : Human readable password generator

Below is a Java version of my previous tutorial on how to generate human readable password. Basically, what this Java program does is to generate a password that look like this "mu27ju" instead of "sdjfasf12gax3ad@mjxsof".

This kind of password is easier to remember when read by text-to-speech software over the phone.

For the best result, keep the number of alphabets to 6 and digits to 2. It should be practical and random enough. Anything beyond that will be hard to read and remember.

Here you go!

 package socketloop;

 import java.security.SecureRandom;

 public class HumanReadablePasswordGenerator {

 private static final String VOWELS = "aeiou";
 private static final String CONSONANTS = "bcdfghjklmnpqrstvwxyz";
 private static final String DIGITS = "0123456789";

 public static void main(String[] args) {

 System.out.format("Password length of 6 with 2 digits in the middle : %s%n", humanReadablePassword(6,2)); // best result
 System.out.format("Password length of 12 with 2 digits in the middle : %s%n", humanReadablePassword(12,2));
 }

 public static String humanReadablePassword(int alphabetSize, int numberSize) {
 // sanity check
 if (alphabetSize < 1) throw new IllegalArgumentException();
 if (numberSize < 1) throw new IllegalArgumentException();

 // initialize  
 char randomCharacter = 'a';
 int character = 0;

 int prefixSize = alphabetSize/2;
 if (alphabetSize%2 != 0) {
 prefixSize = ((int)(alphabetSize/2)) + 1;
 }



 StringBuilder prefixPart = new StringBuilder(prefixSize);

 for (int i = 0; i < prefixSize-1; i++) {
 if (i%2 == 0) {
 // use consonants
 character = (int)(Math.random()*CONSONANTS.length());
 randomCharacter = CONSONANTS.charAt(character);
 prefixPart.append(randomCharacter);
 } else {
 // use vowels
 character = (int)(Math.random()*VOWELS.length());
 randomCharacter = VOWELS.charAt(character);
 prefixPart.append(randomCharacter);
 }
 }

 StringBuilder middlePart = new StringBuilder(numberSize);

 for (int i = 0; i < numberSize; i++) {
 // use digits
 character = (int)(Math.random()*DIGITS.length());
 randomCharacter = DIGITS.charAt(character);
 middlePart.append(randomCharacter);
 }


 int suffixSize = alphabetSize - prefixSize;
 StringBuilder suffixPart = new StringBuilder(suffixSize);

 for (int i = 0; i < suffixSize-1; i++) {
 if (i%2 == 0) {
 // use consonants
 character = (int)(Math.random()*CONSONANTS.length());
 randomCharacter = CONSONANTS.charAt(character);
 suffixPart.append(randomCharacter);
 } else {
 // use vowels
 character = (int)(Math.random()*VOWELS.length());
 randomCharacter = VOWELS.charAt(character);
 suffixPart.append(randomCharacter);
 }
 }

 prefixPart.append(middlePart).append(suffixPart);

 return prefixPart.toString();

 }
 }

Sample output:

Password length of 6 with 2 digits in the middle : mu72ne

Password length of 12 with 2 digits in the middle : yucer20zosuy