Question

I have an ArrayList of doubles, and i need to find the average between all numbers. The amount of Double instances in the arraylist is not constant, could be 2, could be 90 I have been trying for hours to get the algorithm myself but could not get it to work in anyway.

你有什么建议? 或者,你能否把我与现有的图书馆联系起来,以获得这一平均数?

谢谢。

Answer 1

创建<条码>。变量:

double sum = 0;

采用排行方式通过清单中的内容:

for (double d : yourList)

在每一版本中添加<代码>sum。现行价值:

    sum += d;

为找到平均数,将<代码>sum与清单中要素数分开:

double avg = sum / yourList.size();

这里的指认为过于简单的。

上述解决办法实际上并不完美。如果名单上的头几个要素极为庞大,最后几个要素是小的,那么由于两倍的精确性,<代码>sum += d可能不会对最终结果产生任何影响。

解决办法是在进行平均计算之前对清单进行分类:

Collections.sort(doublesList);

Now the small elements will be added first, which makes sure they are all counted as accurately as possible and contribute to the final sum :-)

Answer 2

如果你们喜欢流子的话:

List<Number> list = Arrays.asList(number1, number2, number3, number4);

// calculate the average
double average = list.stream()
                     .mapToDouble(Number::doubleValue)
                     .average()
                     .getAsDouble();

Answer 3

平均定义是所有价值的总和,按价值数目分列。超越价值观,增加这些价值观,按清单的规模划分。

Answer 4

If by "average between all numbers" you mean the average of all the doubles in your list, you can simply add all the doubles in your list (with a loop) and divide that total by the number of doubles in your list.

Answer 5

您:

List<Double> list = new ArrayList<Double>();
...    
double countTotal = 0;

for (Double number : list)
{
    countTotal += number;
}

double average = countTotal / list.size();

Answer 6

也许我要提一下问题......但这不是什么样?

double sum = 0.0;
for (double element : list) {
    sum += element;
}
double average = sum / list.size();

Answer 7

如果你把整个名单一概归一旁,就重新担心过多,你可以使用一个正常的平均数。由于它拥有更多的业务,将比增加所有活动并一劳永逸。

for (int x = 0; x < list.size(); x++)
   average = (average / (x+1)) * (x) + list.get(x) / (x+1);

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