Java uuid generator11/12/2023 Many of the answers discuss how many UUIDs would have to be generated to reach a 50% chance of a collision. Not even with (hypothetical) clever representations. I don't think that is practical for the length of time needed to test for collisions of a high quality RNG. Now multiply that by 1,000,000 and the number of seconds that you are going to run the experiment for. Or the possibility that someone has tinkered with your JRE, either on your system or upstream.)ġ - Assuming that you used "some kind of binary btree" as proposed by an anonymous commenter, each UUID is going to need O(NlogN) bits of RAM memory to represent N distinct UUIDs assuming low density and random distribution of the bits. (And that might include some of the workarounds for "shortage of entropy" problems on some systems. However, if you were to use a JVM with a "broken" crypto- random number generator, all bets are off. But I think we can be confident that if you are using a creditable provider for your cryptographic strength random numbers, then it will be cryptographic strength, and the probability of repeats will be the same as for an ideal (non-biased) random number generator. Now of course, you will typically be using a pseudo-random number generator, not a source of truly random numbers. because of the practical difficulty of looking for collisions. actually noticed) a duplicate in real life are even smaller than vanishingly small. The chances that anyone has experienced (i.e. And to detect the duplicate, you'd have to solve the problem of comparing 1 million new UUIDs per second against all of the UUIDs you have previously generated 1! (The spec says that you lose 2 bits for the type, and a further 4 bits for a version number.)Īssuming that you were to generate 1 million random UUIDs a second, the chances of a duplicate occurring in your lifetime would be vanishingly small. There are 2^122 possible values for a type-4 UUID. Does anybody have any experience to share?
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