Merge two sorted linked lists

ListNode.java

package com.interviewbytes.linkedlists;


public class ListNode {
    int val;
    ListNode next;

    ListNode(int x) {
        val = x;
    }
}

MergeTwoLists.java

package com.interviewbytes.linkedlists;


public class MergeTwoLists {

    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {

        ListNode sentinel = new ListNode(0);
        ListNode current = sentinel;

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

        if (l1 != null) current.next = l1;
        if (l2 != null) current.next = l2;

        return sentinel.next;

    }
}