微信红包的随机算法是怎样实现的？

public static double getRandomMoney(LeftMoneyPackage _leftMoneyPackage) {
    // remainSize 剩余的红包数量
    // remainMoney 剩余的钱
    if (_leftMoneyPackage.remainSize == 1) {
        _leftMoneyPackage.remainSize--;
        return (double) Math.round(_leftMoneyPackage.remainMoney * 100) / 100;
    }
    Random r     = new Random();
    double min   = 0.01; //
    double max   = _leftMoneyPackage.remainMoney / _leftMoneyPackage.remainSize * 2;
    double money = r.nextDouble() * max;
    money = money <= min ? 0.01: money;
    money = Math.floor(money * 100) / 100;
    _leftMoneyPackage.remainSize--;
    _leftMoneyPackage.remainMoney -= money;
    return money;
}

/**
 * @param count 红包数
 * @param money 总金额
 * @return
 */
public static Integer[] ranRedPac(Integer count, Integer money) {
	Integer[] result = new Integer[count];
	for (int i = 1; i <= money; i++) {
		int n = new Random().nextInt(count);
		result[n] = result[n] == null ? 1 : result[n] + 1;
	}
	return result;
}

//测试
public static void main(String[] args) {
	Arrays.asList(ranRedPac(10, 5000000)).forEach(i -> System.out.println(i));
	System.out.println("sum: " + Arrays.asList(ranRedPac(10, 50)).stream().mapToInt(i -> i).sum());
}