Question on Java methods

Question

I got a question. I am given a linked-list Node with the parameter of A val and Node next. I also given a function call join which will join the end of list x to to y.

5 |-> 6 |-> 7 |-> null

Node x = new Node(5, new Node(6, new Node(7, null))); 
this.join(x, x) 
 public void join(Node x, Node y){
 if(x.next==null){
 x.next = y;
 }else{
 join(x.next, y);
 }
}

and when I get the length is only 3. Can I how come is not a stack overflow instead?

• Armand: Can we see the length() method?

Answer 1

how come is not a stack overflow instead?

Because the list still has an end before the call to join() terminates. If you call it again, however...

• shh: Hi thanks for the reply. I check again and it turn out to be overflow.

Answer 2

The join function looks good, but if you invoke it with this.join(x,x) you build some kind of circle!

So if you do something recursive with x after this.join(x,x), you will possible get some kind of stack overflow because of an endless recusrion.

• shh: Hi! thanks for your reply and it indeed turn into an overflow.

Answer 3

Because there is only one instance of node x, and you build up circle in your list. You will never reach x.next==null. You should probably check for some equality.

• shh: Hi thanks.You are right! it was my code that was the problem.