import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
 
class Main {
	public static void main(String[] args) {
		List<List<Integer>> listOfListofInts = Arrays.asList(Arrays.asList(1, 2, 3), Arrays.asList(4, 5, 6), Arrays.asList(7, 8, 9));
		System.out.println(listOfListofInts.stream().flatMap(List::stream).collect(Collectors.toList()));
		System.out.println(listOfListofInts.stream().map(List::stream).collect(Collectors.toList()));
	}
}
 
//https://pt.stackoverflow.com/q/432269/101

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