反转链表后再相加

public class Solution {
    /**
     * 
     * @param head1 ListNode类 
     * @param head2 ListNode类 
     * @return ListNode类
     */
    public ListNode addInList (ListNode head1, ListNode head2) {
        // write code here
        head1 = reverse(head1);
        head2 = reverse(head2);
        ListNode head = new ListNode(-1);
        ListNode cur = head;
        int carry = 0;
        while(head1 != null || head2 != null) {
            int val = carry;
            if (head1 != null) {
                val += head1.val;
                head1 = head1.next;
            }
            if (head2 != null) {
                val += head2.val;
                head2 = head2.next;
            }
            cur.next = new ListNode(val % 10);
            carry = val / 10;
            cur = cur.next;
        }
        if (carry > 0) {
            cur.next = new ListNode(carry);
        }
        return reverse(head.next);
    }

    private ListNode reverse(ListNode head) {
        ListNode cur = head;
        ListNode pre = null;
        while(cur != null) {
            ListNode temp = cur.next;
            cur.next = pre;
            pre = cur;
            cur = temp;
        }
        return pre;
    }
}