@Override
        public double getAmount(@Nonnull Random random) {
            double var = this.variance.getAmount(random);
            return this.base + random.nextDouble() * var * 2 - var;
        }
Represents a base amount with a variance, the final amount will be the
base amount plus or minus a random amount between zero (inclusive) and
the variance (exclusive).
helper/src/main/java/me/lucko/helper/random/VariableAmount.java