Distribution of Random Numbers

Question

I have two options of code:

Option 1

int myFunc() {
  return new Random().nextInt();
}

Or:

Option 2

Answer 1

Java initializes the random seed with System.nanoTime() and a sequential counter. This gives somewhat a guarantee that the seed will be different for each invocation, although I would refrain from calling it cryptographically secure.

From the performance point of view - do you really expect locking on internal state of Random in option 1 to have a larger performance hit then all of the following:

• accessing and incrementing volatile long
• getting the current system time (which is quite expensive)
• dynamic allocation
• another object for garbage collection

My suggestion will be to do benchmarks of your real application to find out, but I expect option 1 to be the slowest of all three.