Combine two sorted linked list

Recursive:
public class Merge{
public LinkedList output;
public void combine(LinkedListNode l1, LinkedListNode l2){
if(l1==null&&l2==null){
return;
}
else if(l1==null){
while(l2){
output.add(l2);
l2=l2.next;
}
}
else if(l2==null){}

else{
if(l1.value<l2.value){
output.add(l1);
combine(l1.next, l2);
}
else{
output.add(l2);
combine(l1,l2.next);
}
}
return;
}
}