I came up with below solution, not sure if Type:safety warnings can be removed using something else.
BiFunction<List<List<T>>, Class<T>,T[][]> toArray = (list,type) ->
{
T a[][] = (T[][]) Array.newInstance(type,
list.size(), list.get(0).size());
IntStream.range(0, a.length)
.forEach(i -> {
a[i]=(T[]) list.get(i).toArray();
});
return a;
};
Also, if this could be improved with one single pipeline I would appreciate the solution.
I have two suggestions, in both, convert the from List to List iterating List of List and adding each element as T[] in a new list.
Use Array.newInstance only for create auxiliar objects and add @SuppressWarnings annotation
@SuppressWarnings("unchecked")
public static <T> T[][] toArray(List<List<T>> list, Class<T> type) {
T aux[] = (T[]) Array.newInstance(type, 0);
T auxBi[][] = (T[][]) Array.newInstance(type, 0, 0);
List<T[]> newList = new ArrayList<>();
list.forEach(e -> newList.add(e.toArray(aux)));
T[][] newBi = newList.toArray(auxBi);
return newBi;
}
or
add auxliars as parameters instead of type
public static <T> T[][] toArray(List<List<T>> list, T aux[], T auxBi[][]) {
List<T[]> newList = new ArrayList<>();
list.forEach(e -> newList.add(e.toArray(aux)));
T[][] newBi = newList.toArray(auxBi);
return newBi;
}
public BiFunction<List<List<T>>,Class<T>, T[][]> toArr = (list,type)-> list.stream().map(row -> row.toArray((T[]) Array.newInstance(type, 0))).collect(Collectors.toList()).toArray((T[][]) Array.newInstance(type, 0, 0));
List.toArray()without an argument will always returnObject[]- you'll need to create proper instances for the components as well, not just for the larger array. Where do you get your warnings?List<List<T>>toT[][]BiFunction<List<List<T>>, Class<T>,T[][]> toArray = (list,type) -> { T a[][] = (T[][]) Array.newInstance(list.get(0).get(0).getClass(), list.size(), list.get(0).size()); IntStream.range(0, list.size()) .forEach(i -> { IntStream.range(0, list.get(0).size()) .forEach(j -> { a[i][j]=list.get(i).get(j); }); }); return a; };