static final private String ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; final private Random rng = new SecureRandom(); char randomChar(){ return ALPHABET.charAt(rng.nextInt(ALPHABET.length())); } String randomUUID(int length, int spacing, char spacerChar){ StringBuilder sb = new StringBuilder(); int spacer = 0; while(length > 0){ if(spacer == spacing){ sb.append(spacerChar); spacer = 0; } length--; spacer++; sb.append(randomChar()); } return sb; }