Merge Two Sorted Lists

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if(l1 == null && l2 == null ) return l1;
        if(l1 == null) return l2;
        if(l2 == null) return l1;
        ListNode dummy = new ListNode(0);
        ListNode tail = dummy;
        tail = dummy;

        while(l1 != null && l2 != null){
            if( l1.val < l2.val){
                tail.next = l1;
                l1 = l1.next;
            }else{
                tail.next = l2;
                l2 = l2.next;               
            }
            tail = tail.next;
        }
        if(l1 != null) tail.next = l1;
        if(l2 != null) tail.next = l2;
        return dummy.next;

    }
}