Question

In this code:

Random random = new Random(441287210);
for(int i=0;i<10;i++)
    System.out.print(random.nextInt(10)+" ");
}

The output is 1 1 1 1 1 1 1 1 1 1, every time.

Why is this? Isn’t Random supposed to be… well… random? I thought that the Random class use System.nanoTime, so the output should be generally random. Can someone please explain?

Answer 1

The values generated by Random class are pseudo-random: they are created using a deterministic algorithm, based on seed value. Typically (if you use parameterless constructor, for example) the seed is initialized using current time, which is obviously a unique value. Hence a unique, ‘random’ sequence is generated.

Here you are using a constant seed value which doesn’t change between executions of your code. Therefore you always get the same sequence. It just happens that this sequence is 1 1 1 1 1 1 ... for this particular seed.