@Override
        public boolean equals(Object o) {
            if (o == this) return true;
            if (!(o instanceof Fixed)) return false;
            final Fixed other = (Fixed) o;
            return Double.compare(this.amount, other.amount) == 0;
        }
Represents a fixed amount, calls to {@link #getAmount} will always return
the same fixed value.
helper/src/main/java/me/lucko/helper/random/VariableAmount.java