Question

According to the documentation:

When this method is first called, it creates a single new pseudorandom-number generator, exactly as if by the expression

new java.util.Random

This new pseudorandom-number generator is used thereafter for all calls to this method and is used nowhere else.

I’m confused as to the scope of ‘When this method is first called” – is it when my application first calls it? Is it only ever seeded once no matter what my application does?

Answer 1

When it is first called in your JVM (by any code).

It’s doing an (unsafe – see link below) lazy initialization of a singleton:

private static Random randomNumberGenerator;

by calling:

private static synchronized void initRNG() {
    if (randomNumberGenerator == null) 
        randomNumberGenerator = new Random();
}

EDIT Note that this code is not thread safe. Official bug: https://bugs.java.com/bugdatabase/view_bug?bug_id=6470700