import java.util.*;

public class Ex13Reverse3 {

	public static void reverse3(ArrayList<Integer> list) {
		for (int i = 0; i < list.size(); i+=3) {
			if (i + 2 < list.size()) {
				Integer n1 = list.get(i);
				Integer n3 = list.get(i+2);
				list.set(i, n3);
				list.set(i+2, n1);
			}
		}
	}
	
	public static void main(String[] args) {
		Integer[] nums = { 3, 8, 19, 42, 7, 26, 19, -8 }; 
		ArrayList<Integer> list = new ArrayList<Integer>(
			Arrays.asList(nums)
		);
		System.out.println(list.toString());
		reverse3(list);
		System.out.println(list.toString());
	}

}