public List<BigDecimal> divideRedPacket(BigDecimal totalAmount, int num) { List<BigDecimal> list = new ArrayList<>(); BigDecimal remainingAmount = totalAmount; Random random = new Random(); for (int i = 0; i < num; i++) { if (i == num - 1) { list.add(remainingAmount); } else { BigDecimal maxAmount = remainingAmount.divide(new BigDecimal(num - i), 2, BigDecimal.ROUND_DOWN) .multiply(new BigDecimal("2")); BigDecimal amount = maxAmount.multiply(new BigDecimal(random.nextDouble() + 0.01)) .setScale(2, BigDecimal.ROUND_DOWN); list.add(amount); remainingAmount = remainingAmount.subtract(amount); } } return list; }优化以上代码，要求添加两个参数，两个参数分别控制几个红包的小数点第二位为几

可以通过将小数点第二位按照要求进行舍入来实现。优化后的代码如下：

public List<BigDecimal> divideRedPacket(BigDecimal totalAmount, int num, int scale) {
    List<BigDecimal> list = new ArrayList<>();
    BigDecimal remainingAmount = totalAmount;
    Random random = new Random();
    for (int i = 0; i < num; i++) {
        if (i == num - 1) {
            list.add(remainingAmount.setScale(scale, BigDecimal.ROUND_DOWN));
        } else {
            BigDecimal maxAmount = remainingAmount.divide(new BigDecimal(num - i), scale + 1, BigDecimal.ROUND_DOWN)
                    .multiply(new BigDecimal("2"));
            BigDecimal amount = maxAmount.multiply(new BigDecimal(random.nextDouble() + 0.01))
                    .setScale(scale, BigDecimal.ROUND_DOWN);
            list.add(amount);
            remainingAmount = remainingAmount.subtract(amount);
        }
    }
    return list;
}

其中，第三个参数 `scale` 控制小数点第二位为 `scale`。在计算最大金额时，将小数点精度设为 `scale + 1`，然后再通过 `.setScale(scale, BigDecimal.ROUND_DOWN)` 将小数点第二位舍入为 `scale`。在计算实际金额时，直接通过 `.setScale(scale, BigDecimal.ROUND_DOWN)` 将小数点第二位舍入为 `scale`。