Java Random Numbers with Fixed Seed: Why Identical Outputs?

In your code, you've defined a method to generate random numbers using a specified seed. However, you're noticing that when you provide the same seed, all 100 generated numbers are identical.

This behavior is expected because using the same seed in the Random constructor results in a predictable sequence of numbers. A seed is a seed value that initializes the random number generator. This is an important feature for testing, as it allows for consistent results when rerunning tests.

Understanding Pseudorandom Number Generation

Pseudorandom number generators (PRNGs) like Random in Java generate sequences that are close to true randomness. However, they have a small set of initial values, including the seed, which completely determines the sequence.

Fixing the Code

To generate different sequences of random numbers, you should avoid using the same seed each time. Instead, create a Random instance outside of your method and initialize it with no arguments. This instance will use the nanoTime method to generate a unique seed value.

Here's the corrected code:

private Random generator = new Random();
double randomGenerator() {
    return generator.nextDouble() * 0.5;
}

With this change, you'll get different sequences of random numbers every time you call the randomGenerator method.