import java.util.ArrayList; import java.util.Iterator; import java.util.Scanner; public class HackerrankJava0049 { @SuppressWarnings({ "unchecked" }) public static void main(String[] args) { // Java Iterator // https://www.hackerrank.com/challenges/java-iterator/problem?isFullScreen=true ArrayList mylist = new ArrayList(); Scanner sc = new Scanner(System.in); int n = sc.nextInt(); int m = sc.nextInt(); for (int i = 0; i < n; i++) { mylist.add(sc.nextInt()); } mylist.add("###"); for (int i = 0; i < m; i++) { mylist.add(sc.next()); } Iterator it = func(mylist); while (it.hasNext()) { Object element = it.next(); System.out.println((String) element); } } static Iterator func(ArrayList mylist) { Iterator it = mylist.iterator(); while (it.hasNext()) { // --- You need to update this line --- Object element = it.next(); // --- You need to update this line --- if (element instanceof String) break; } return it; } }