1290. Convert Binary Number in a Linked List to Integer

class Solution {
    public int getDecimalValue(ListNode head) {
        int num = 0;
        while (head != null) {
            num = (num << 1) | head.val;  
            head = head.next;
        }
        return num;
    }
    public static ListNode createLinkedList(int[] arr) {
        if (arr.length == 0) {
            return null;
        }

        ListNode head = new ListNode(arr[0]);
        ListNode current = head;

        for (int i = 1; i < arr.length; i++) {
            current.next = new ListNode(arr[i]);
            current = current.next;
        }

        return head;
    }
}