import java.util.*;

public class Ex16Interleave {

	public static void interleave(ArrayList<Integer> list1, ArrayList<Integer> list2) {
		int j = 0;
		for (int i = 0; i < list1.size() && j < list2.size(); i++,j++) {
			Integer n = list2.get(j);
			list1.add(i+1,n);
			i++;
		}
		// if list2 is longer than list1, j will be < list2.size() 
		// in that case, you'll append list2's remaining elements
		for (; j < list2.size(); j++) {
			Integer n = list2.get(j);
			list1.add(n);
		}
	}

	public static void main(String[] args) {
		Integer[] a1 = { 10, 20, 30 };  
		ArrayList<Integer> list1 = new ArrayList<Integer>(
				Arrays.asList(a1)
				);
		Integer[] a2 = { 4, 5, 6, 7, 8 }; 
		ArrayList<Integer> list2 = new ArrayList<Integer>(
				Arrays.asList(a2)
				);
		Integer[] a3 = { 10, 20, 30, 40, 50 };  
		ArrayList<Integer> list3 = new ArrayList<Integer>(
				Arrays.asList(a3)
				);
		Integer[] a4 = { 6, 7, 8 }; 
		ArrayList<Integer> list4 = new ArrayList<Integer>(
				Arrays.asList(a4)
				);
		System.out.println(list1.toString());
		System.out.println(list2.toString());
		interleave(list1, list2);
		System.out.println(list1.toString());

		System.out.println();

		System.out.println(list3.toString());
		System.out.println(list4.toString());
		interleave(list3, list4);
		System.out.println(list3.toString());
	}

}