有没有一种快速的方法可以对List< List<Double> >
求平均值,所以我只有一个Double列表,其中每一列都是该列中所有原始列表的平均值?
最佳答案
使用Java 8,您可以编写类似这样的内容-尽管它并不短...
List<List<Double>> list = Arrays.asList(Arrays.asList(1d, 2d, 3d),
Arrays.asList(2d, 3d, 4d, 5d));
//the largest list size
int maxSize = list.stream().mapToInt(List::size).max().orElse(0);
//for each index in the final list, we calculate the average across "valid" lists
//i.e. lists that are large enough
List<Double> averages = IntStream.range(0, maxSize)
.mapToObj(i -> list.stream()
.filter(sublist -> sublist.size() > i)
.mapToDouble(sublist -> sublist.get(i))
.average().getAsDouble())
.collect(toList());
//prints averages = [1.5, 2.5, 3.5, 5.0]
System.out.println("averages = " + averages);