javarandomrandom-seed

Set seed on Math.random()

I need to write some junit tests on Java code that calls Math.random(). I know that I can set the seed if I was instantiating my own Random object to produce repeatable results. Is there a way to do this also for Math.random() ?

Solution

  • The method Math.random() uses a private static field:

    private static Random randomNumberGenerator;

    If you really really need to set this to a new Random(CONSTANT_SEED) (for instance you need to JUNit test code which you have no control over) you could do so by using reflection.