java fill two dimensional array stream

To fill a two-dimensional array with data using a Stream in Java, you can use the map() method to transform each element of the stream into an array, and then use the toArray() method to collect the elements into a two-dimensional array.

Here's an example of how to do it:

import java.util.Arrays;
import java.util.List;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class Main {
  public static void main(String[] args) {
    // Create a list of lists
    List<List<Integer>> list = Arrays.asList(
      Arrays.asList(1, 2, 3),
      Arrays.asList(4, 5, 6),
      Arrays.asList(7, 8, 9)
    );

    // Convert the list to a stream and map each element to an array
    Stream<int[]> stream = list.stream().map(l -> l.stream().mapToInt(i -> i).toArray());

    // Collect the stream into a two-dimensional array
    int[][] array = stream.toArray(int[][]::new);

    // Print the array
    for (int[] row : array) {
      System.out.println(Arrays.toString(row));
    }
  }
}

This code creates a list of lists, and then converts it to a stream of arrays using the map() method. The toArray() method is used to collect the elements of the stream into a two-dimensional array.

Note that the toArray() method takes a IntFunction as an argument, which is used to create the array. In this case, we use int[][]::new to create a two-dimensional array of ints.

You can use a similar approach to fill a two-dimensional array with any type of data, as long as you use the appropriate method to convert the data to an array.