How to Generate Non-Deterministic Random Numbers in Java When Using a Fixed Seed?

Generating Random Numbers with a Fixed Seed in Java

When generating random numbers using a seed, it's essential to understand how seeds influence the randomness. By providing the same seed as an argument to a Random object, the generated sequence of numbers will be reproducible and deterministic. This is a desirable feature for unit testing or replicating specific scenarios.

The provided code uses a fixed seed to create a Random object. This ensures that every time 100 numbers are generated with the same seed, they will be identical. To fix this and generate different sequences, consider the following approaches:

1. Remove the Seed Argument:
   Calling the zero-argument constructor of Random, which uses the current nanotime as the seed, allows for different seed values with each invocation.
2. Generate Random Seeds:
   If true randomness is crucial, use other sources like UUIDs or a secure random number generator (e.g., java.security.SecureRandom) to generate the seed dynamically.
3. Keep Random Instance Outside:
   Create a single Random instance outside the method and reuse it to generate all random numbers. This ensures that the seed is only set once and subsequent calls to randomGenerator() use the same seed.

For example, the code below modifies the provided code to implement the first approach:

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

By removing the seed argument, this code generates different sequences of random numbers with each invocation. Remember that deterministic randomness is important for testing and consistency. True randomness may be desirable in some use cases, so choose the approach that best suits your requirements.

The above is the detailed content of How to Generate Non-Deterministic Random Numbers in Java When Using a Fixed Seed?. For more information, please follow other related articles on the PHP Chinese website!