problem with Random.nextGaussian()

Question

Random.nextGaussian() is supposed to give random no.s with mean 0 and std deviation 1. Many no.s it generated are outside range of [-1,+1]. how can i set so that it gives n

Answer 1

This code will display count number of random Gaussian numbers to console (10 in a line) and shows you some statistics (lowest, highest and average) afterwards.

If you try it with small count number, random numbers will be probably in range [-1.0 ... +1.0] and average can be in range [-0.1 ... +0.1]. However, if count is above 10.000, random numbers will fall probably in range [-4.0 ... +4.0] (more improbable numbers can appear on both ends), although average can be in range [-0.001 ... +0.001] (way closer to 0).

public static void main(String[] args) {
    int count = 20_000; // Generated random numbers
    double lowest = 0;  // For statistics
    double highest = 0;
    double average = 0;
    Random random = new Random();

    for (int i = 0; i < count; ++i) {
        double gaussian = random.nextGaussian();
        average += gaussian;
        lowest = Math.min(gaussian, lowest);
        highest = Math.max(gaussian, highest);
        if (i%10 == 0) { // New line
            System.out.println();
        }
        System.out.printf("%10.4f", gaussian);
    }
    // Display statistics
    System.out.println("\n\nNumber of generated random values following Gaussian distribution: " + count);
    System.out.printf("\nLowest value:  %10.4f\nHighest value: %10.4f\nAverage:       %10.4f", lowest, highest, (average/count));
}