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

class RedPackage {
    int    remainSize;
    double remainMoney;
}

static void init() {
    redPackage.remainSize  = 30;
    redPackage.remainMoney = 500;
}

// 第一次
15.69   21.18   24.11   30.85   0.74    20.85   2.96    13.43   11.12   24.87   1.86    19.62   5.97    29.33   3.05    26.94   18.69   34.47   9.4 29.83   5.17    24.67   17.09   29.96   6.77    5.79    0.34    23.89   40.44   0.92
// 第二次
10.44   18.01   17.01   21.07   11.87   4.78    30.14   32.05   16.68   20.34   12.94   27.98   9.31    17.97   12.93   28.75   12.1    12.77   7.54    10.87   4.16    25.36   26.89   5.73    11.59   23.91   17.77   15.85   23.42   9.77

/**
 * 并不完美的红包算法
 */
public static double rand(double money, int people, List<Double> l) {
    if (people == 1) {
        double red = Math.round(money * 100) / 100.0;
        l.add(red);
        return 0;
    }
    Random random = new Random();
    double min = 0.01;
    double max = money / people * 2.0;
    double red = random.nextDouble() * max;
    red = red <= min ? min : red;
    red = Math.floor(red * 100) / 100.0;
    l.add(red);
    double remain = Math.round((money - red) * 100) / 100.0;
    return remain;
}

public static double rand(double money, int people, List<Double> l) {
    if (people == 1) {
        double red = Math.round(money * 100) / 100.0;
        l.add(red+0.01);
        return 0;
    }
    Random random = new Random();
    double min = 0;
    double max = money / people * 2.0;
    double red = random.nextDouble() * max;
    red = red <= min ? min : red;
    red = Math.floor(red * 100) / 100.0;
    l.add(red+0.01);
    double remain = Math.round((money - red) * 100) / 100.0;
    return remain;
}

_money = _money - people * 0.01;