Here's a quick way to generate a short, random string in Java:
Random r = new Random(); String token = Long.toString(Math.abs(r.nextLong()), 36);
The resultant string is a maximum of
ceil(ln(263) / ln(36)) = 13 characters long and is suitable for use as a temporary id or cookie name.
An even quicker and dirtier method is to simply convert a random double to a string:
String token = "token" + Math.random();
This is useful in test cases and one-offs, but I wouldn't put it into production code.