code: public static String uuid() {
  		char[] uuid = new char[36];
  		uuid[8] = uuid[13] = uuid[18] = uuid[23] = '-';
  		for (int i = 0; i < 36; i++) {
  			if (uuid[i] == 0) {
  				uuid[i] = UUID.CHARS[UUID.randomInt(16)];
  			}
  		}
  		return new String(uuid);
  	}
docs: Generate an UUID looks like RFC4122 v4.
  <p>
  <strong>Example : </strong>D8DA62A2-9844-D4F6-0120-73D61116ED45
  </p>
  
  @return the unique id string