{

public static void main(String[] args)

{

//Converting nested lists into List using flatMap()

List<Integer> list1 = Arrays.asList(1,2,3);

List<Integer> list2 = Arrays.asList(4,5,6);

List<Integer> list3 = Arrays.asList(7,8,9);

List<List<Integer>> listOfLists = Arrays.asList(list1, list2, list3);

List<Integer> listOfAllIntegers = listOfLists.stream()

.flatMap(x -> x.stream())

.collect(Collectors.toList());

System.out.println(listOfAllIntegers);

//Converting nested Arrays into list using flatMap()

String[][] arr = new String[][]{{"a", "b"}, {"c", "d"}, {"e", "f"}, {"g", "h"}};

List<String> listOfAllChars = Arrays.stream(arr)

.flatMap(x -> Arrays.stream(x))

.collect(Collectors.toList());

System.out.println(listOfAllChars);

}

}