How do you get a instance of `kotlin.random.Random...

# stdlib

[karelpeeters]

How do you get a instance of kotlin.random.Random? I don't want to use the Random.Default since this is in a multithreaded context. The docs (https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.random/-random/index.html) say

To get a seeded instance of random generator use Random function.

But that Random function just links back to the same page. Am I missing something?

[elizarov]

I don’t understand the problem you have with Random.Default.

[karelpeeters]

I don't want to pay for the multithreaded safety, I need a lot of random numbers on different threads.

[elizarov]

And why do you think you have to pay for the threadsafety if you use it from different threads?

[elizarov]

I’m really curious. In fact, it is backed by thread-local random implementation (on JDK7+) so it does not matter how many threads concurrently use it.

[karelpeeters]

Ah I see, I thought it was backed by a single Random instance with locks. Where can I find the JVM implementation?

[ilya.gorbunov]

See https://github.com/JetBrains/kotlin/blob/v1.3.30/libraries/stdlib/jdk8/src/kotlin/random/jdk8/PlatformThreadLocalRandom.kt
A correction: we use ThreadLocalRandom on JDK 8+ and if you have kotlin-stdlib-jdk8 in dependencies.

[karelpeeters]

Got it, thanks!