Add Two Numbers 2.java

import java.math.BigInteger;
/**
 * Definition for singly-linked list.
 * public class ListNode {
 * int val;
 * ListNode next;
 * ListNode() {}
 * ListNode(int val) { this.val = val; }
 * ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        String first = "";
        String second = "";
        ListNode newPointer = new ListNode();

        ListNode pointer = l1;
        while (pointer != null) {
            first += pointer.val;
            pointer = pointer.next;
        }

        pointer = l2;
        while (pointer != null) {
            second += pointer.val;
            pointer = pointer.next;
        }

        BigInteger num1 = new BigInteger(first);
        BigInteger num2 = new BigInteger(second);
        BigInteger sum = num1.add(num2);
        String total = sum.toString();

        if (total.length() > first.length() && total.length() > second.length()) {
            ListNode newNode;
            int i = 1;
            if (first.length() > second.length()) {
                newPointer =l1;
                pointer = l1;
            }else{
                newPointer =l2;
                pointer = l2;
            }
            while (pointer != null) {
                    pointer.val = Character.getNumericValue(total.charAt(i));
                    pointer = pointer.next;
                    i++;
                }
            newNode = new ListNode(Character.getNumericValue(total.charAt(0)),newPointer);
            return newNode;
            }


    if(first.length()>second.length())
    {
        newPointer = l1;
        pointer = l1;
    }else
    {
        newPointer = l2;
        pointer = l2;
    }
    int i = 0;while(pointer!=null)
    {
        pointer.val = Character.getNumericValue(total.charAt(i));
        pointer = pointer.next;
        i++;
    }return newPointer;

}}