How good is Java's UUID.randomUUID?

Confidence in UUID.randomUUID

Java’s UUID.randomUUID() internally depends on java.security.SecureRandom, famous for its cryptographically strong random number generation (RNG). This imposes formidable grounds for UUID uniqueness, passing even stringent statistical RNG tests.

Your faith in RNG resembles your faith in this method - producing duplicate UUID is like spotting a unicorn, rare and statistically almost impossible.

Caveats and subtleties

However, like any good ghost story, a slight chance of error exists. Implementation bugs, JVM's RNG issues can challenge the promised uniqueness. Always make sure to presuppose reliable RNG providers, and keep updated about known issues in their implementation.

Proven reliability

In reality, UUID.randomUUID() has consistently shown reliable and impressive results. Detecting a duplicate is like pinpointing a single specific atom in the universe. The real-world data upholds the dependable low collision rate, thereby reinforcing faith in the overall UUID system.

Taking it up a notch

For stringent requirements, you could test drive functionalities like UuidUtil.getTimeBasedUuid, an approach preferred by Log4j 2. It could possibly lower your collision rate, if you're prepared to sacrifice a bit of simplicity for extra reliability.

Limitations and your pursuit of perfect randomness

While this seems like a perfect Random Factory, our real-world limitations - memory, time or your patience - limit our testing for collisions to theoretical models like binary B-trees.

Don't stress out if every gobstopper doesn't seem different, it's still 'random enough' for most of us.

When random is not truly random

Sharpening the distinction further, it's important to separate UUID.randomUUID() and true random sources. Yes, a little tedious, but SecureRandom is still a pseudo-random number generator. However, the practical differences in collision probabilities are minimal, and more information is available on resources like Wikipedia.

Deep dive into UUID generation methods

When cherry-picking your UUID generation strategy, remember to balance between simplicity and reliability. UuidUtil.getTimeBasedUuid could offer better collision resistance but demands some compromise on simplicity. It all boils down to your priority - a perfect gobstopper, or a quicker tour of the factory.

Scaling UUID in large systems

Consider a corporate behemoth with databases of petabyte-scale. Even in such large systems, the inherent UUID namespace promises almost zero collisions. UUID.randomUUID() thus proves to be a reliable method even at this scale.