Java 8 Stream IllegalStateException: Stream has already been operated on or closed

Question

I\'m trying to generate Order instances using the Stream API. I have a factory function that creates the order, and a DoubleStream is used to initialize the amount of the o

Answer 1

As fge states, you can't (shouldn't) consume a Stream more than once.

Any idea how to fix this?

From the Javadoc of Random#doubles(double, double)

A pseudorandom double value is generated as if it's the result of calling the following method with the origin and bound:

double nextDouble(double origin, double bound) {
    double r = nextDouble();
    r = r * (bound - origin) + origin;
    if (r >= bound) // correct for rounding
       r = Math.nextDown(bound);
    return r;
}

Implement such a method and use it to get a new double value each time you need one instead of trying to get it from a DoubleStream. Possibly use a DoubleSupplier.

private final Random random = new Random();
private DoubleSupplier supplier = () -> nextDouble(random, 50.0, 200.0);

private Order createOrder() {

    return new Order(supplier.getAsDouble());
}

private static double nextDouble(Random random, double origin, double bound) {
    double r = random.nextDouble();
    r = r * (bound - origin) + origin;
    if (r >= bound) // correct for rounding
        r = Math.nextDown(bound);
    return r;
}

If you're not going to reuse the nextDouble method, you can inline the values 50.0 and 200.0.