[英]How to convert nested ArrayList in Array?
I have to convert an ArrayList of ArrayList in to Array.我必须将 ArrayList 的 ArrayList 转换为 Array。
List<List<TockaXY>> clustersPorazdeljeni = new ArrayList<>(centers.size());
I know that is possible to convert a single ArrayList to Array like我知道可以将单个 ArrayList 转换为 Array 之类的
TockaXY[] arrayOfClusters = clustersPorazdeljeni.toArray(new TockaXY[centers.size()]);
But these does not convert the nested part.但是这些不会转换嵌套部分。 As i understand is now array of ArrayLists.
据我所知,现在是 ArrayLists 数组。 So is it possible to get an Array out of nested ArrayLists?
那么是否有可能从嵌套的 ArrayLists 中获取一个 Array?
You can use flatMap: 您可以使用flatMap:
List<List<TockaXY>> clustersPorazdeljeni = new ArrayList<>();
TockaXY[] flattened = clustersPorazdeljeni.stream()
.flatMap(x -> x.stream())
.toArray(x -> new TockaXY[0]);
It is possible using Java Stream
and Stream::flatMap
: 可以使用Java
Stream
和Stream::flatMap
:
List<List<TockaXY>> clustersPorazdeljeni = new ArrayList<>();
TockaXY[] strings = clustersPorazdeljeni.stream()
.flatMap(Collection::stream)
.toArray(TockaXY[]::new);
There is linear alternative for flatMap(): flatMap()有线性替代方案:
List<List<TockaXY>> clustersPorazdeljeni = new ArrayList<>();
List<TockaXY> flatArray = new ArrayList<>();
clustersPorazdeljeni.forEach(flatArray::addAll);
TockaXY[] arrayOfClusters = flatArray.toArray(new TockaXY[0]);
Or with flatMap: 或使用flatMap:
TockaXY[] arrayOfClusters = clustersPorazdeljeni.stream().flatMap(Collection::stream).toArray(TockaXY[]::new);
ArrayList<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
list.add(4);
list.add(5);
Object[] array = list.toArray();
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.