Answer by neuhaus for How to generate a random alpha-numeric string?

You can use the UUID class with its getLeastSignificantBits() message to get 64bit of Random data, then convert it to a radix 36 number (i.e. a string consisting of 0-9,A-Z):

Long.toString(Math.abs( UUID.randomUUID().getLeastSignificantBits(), 36));

This yields a String up to 13 characters long. We use Math.abs() to make sure there isn't a minus sign sneaking in.