Check out example codes for "Lists inside lists in java". It will help you in understanding the concepts better.

Code Example 1

public class GuiTest {

	
	public static void main(String[] args) {
		List<List<Integer>> MainList = new ArrayList<List<Integer>>();
		Random NewRandomNumber = new Random();
		
		for (int i = 0; i < 10; i++) {
			List<Integer> SecondList = new ArrayList<Integer>();
			MainList.add(SecondList);
			for (int i2 = 0; i2 < 10; i2++) {
				SecondList.add(NewRandomNumber.nextInt(6));
			}
		}

Learn ReactJs, React Native from akashmittal.com