How to transpose List<List>?
This is called transposition. The following snippet does what you need:
import java.util.*;
public class ListTranspose {
public static void main(String[] args) {
Object[][] data = {
{ "Title", "Data1", "Data2", "Data3" },
{ "A", 2, 3, 4 },
{ "B", 3, 5, 7 },
};
List<List<Object>> table = new ArrayList<List<Object>>();
for (Object[] row : data) {
table.add(Arrays.asList(row));
}
System.out.println(table); // [[Title, Data1, Data2, Data3],
// [A, 2, 3, 4],
// [B, 3, 5, 7]]"
table = transpose(table);
System.out.println(table); // [[Title, A, B],
// [Data1, 2, 3],
// [Data2, 3, 5],
// [Data3, 4, 7]]
}
static <T> List<List<T>> transpose(List<List<T>> table) {
List<List<T>> ret = new ArrayList<List<T>>();
final int N = table.get(0).size();
for (int i = 0; i < N; i++) {
List<T> col = new ArrayList<T>();
for (List<T> row : table) {
col.add(row.get(i));
}
ret.add(col);
}
return ret;
}
}
See also
- Wikipedia/Transpose
Here is my solution.Thanks to @jpaugh's code.I hope this will help you.^_^
public static <T> List<List<T>> transpose(List<List<T>> list) {
final int N = list.stream().mapToInt(l -> l.size()).max().orElse(-1);
List<Iterator<T>> iterList = list.stream().map(it->it.iterator()).collect(Collectors.toList());
return IntStream.range(0, N)
.mapToObj(n -> iterList.stream()
.filter(it -> it.hasNext())
.map(m -> m.next())
.collect(Collectors.toList()))
.collect(Collectors.toList());
}
This called a transpose operation. A code sample is here, , but will need significant modification as you have an ArrayList of Arrays (what I infer from your question)