This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
You could implement your own random number generator. But beware that it is not easy to create "good" random numbers (random numbers which are truly random, or which at least have a statistical distribution that comes close to being really random). Several algorithms have been invented to generate pseudo-random numbers; do some research to learn more about them.