/* package whatever; // don't place package name! */
 
import java.util.*;
import java.util.stream.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		List<List<Integer>> data = new ArrayList<List<Integer>>();
		data.add(Arrays.asList(1, 2, 3));
		data.add(Arrays.asList(4, 5, 6));
		int[][] res = data.stream().map(l -> l.stream().mapToInt(v -> v).toArray()).toArray(int[][]::new);
		for (int i = 0 ; i != res.length ; i++) {
			for (int v : res[i]) {
				System.out.print(v + " ");
			}
			System.out.println();
		}
 
	}
}

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