main method is not allowed to be altered and no parameters in the ListNode object

A LinkedIntList stores a list of the 2 public class LinkedIntlist { 3 private ListNode front; doubleUp 5 6 7 Write a method doubleUp that doubles the size of a list by inserting a copy of every integer in the list immediately after its original occurrence in the list. Suppose a list stores the values: public void doubleUp() { ListNode current = front; while (current ! null) { ListNode current2 = current ListNode duplicate new ListNode(); 9 13 (1.8, 194, 17 After calling list.doubleUp()the list should store the values: 11, 1, 4, 8, 19, 19, 4, 4, 17, 171 You should only create new nodes when necessary. In the above example, only 5 new nodes should be created during after the call to list.doubleup) 12 13 14 15 public static void main(String[] args) { 16 LinkedIntlist list - new LinkedIntList(1, 8, list.doubleUp(); 18 System.out.println(list); LO ) 20 /home/linkedinti wa 11:9 Spaces: 4 (Auto) Feedback Run Console 1 2 3 4 Not yet TESTCASES 0/1 passed doubleUp: [1.2.3).doubleUp