Konversi List<List<String>> ke String[][]

ListUtil.java

import java.util.List;

import static java.util.Arrays.asList;

public class ListUtil {

    public static String[][] listToArray(List<List<String>> listOfString) {
        String[][] retval = new String[listOfString.size()][];
        int index = 0;
        for (List<String> data : listOfString) {
            String[] array = new String[data.size()];
            data.toArray(array);
            retval[index] = array;
            index++;
        }

        return retval;
    }

    public static void main(String[] args) {
        List<List<String>> data = asList(
                asList("ak", "aw"),
                asList("wa")
        );

        String[][] arrayOfData = listToArray(data);
        int x = arrayOfData.length;
        for (int i = 0; i < x; i++) {
            if (null != arrayOfData[i]) {
                int y = arrayOfData[i].length;
                for (int j = 0; j < y; j++) {
                    System.out.print(arrayOfData[i][j] + "\t");
                }
                System.out.println();
            }
        }
    }
}