How to generate “random” but also “unique” numbers?

Question

How are random numbers generated.? How do languages such as java etc generate random numbers, especially how it is done for GUIDs.? i found that algorithms like Pseudorandomnumb

Answer 1

You could use this code sample: http://xkcd.com/221/ Or, you can use this book: http://www.amazon.com/Million-Random-Digits-Normal-Deviates/dp/0833030477

But seriously, don't implement it yourself, use an existing library. You can't be the first person to do this.