I am working on a singly linked list iterator and during debugging it won't get passed a for loop and i'm stuck as to why.
Here is my Iterator and Node:
class Node<E> {
E data;
Node<E> next;
public Node(E obj){
data = obj;
next = null;
} //end class node
}
private Node<E> head,tail;
int currentSize = 0;//initializes the size to 0
class IteratorHelper implements Iterator<E>{
private Node<E> iteratorptr;
public IteratorHelper(){
this.iteratorptr = head;
}
public boolean hasNext(){
return iteratorptr != null && iteratorptr.next != null;
}
public E next(){
if(!hasNext())
return null;
iteratorptr = iteratorptr.next;
return iteratorptr.data;
}
public void remove(){
throw new UnsupportedOperationException();
}
}
To test the iterator and my linked list implementation my instructor gave me this:
// check the list with the iterator. If n = 25, this should print
// 25 24 23 22 21 ... 5 4 3 2 1
System.out.println("Using the iterator");
for (Integer i : llist)
System.out.print(i + " ");
System.out.println();
And this prints out the desired 25...1 result however when my iterator runs into problems is after I empty the list and add 1 item to it:
// now add one thing to the list
llist.addLast(n+1);
// this should be the only thing in the list
for (int i : llist)
if (i != (n+1))
System.err.println("There should be only one thing in the list, but we got " + i);
During debugging it gets stuck in the for loop indefinitely with i = 26 and never changing.
I have tried to modify my iterator but haven't had any success.
This is my first post on Stack and I am sorry for any bad-posting practices! Thank you for your time!
Edit:
Here is my Node Class: And in a different assignment I have confirmed that it works using a different test file.
class Node<E> {
E data;
Node<E> next;
public Node(E obj){
data = obj;
next = null;
} //end class node
}
And these are my remove methods:
public E removeFirst() {
if (head == null)
return null;
E tmp = head.data;
if (head == tail)
head = tail = null;
else {
head = head.next;
}
currentSize--;
return tmp;
}
public E removeLast() {
Node<E> previous = head;
if (head == null)
return null;
E temp = tail.data;
if (head.next == null)
head = tail = null;
else {
while (previous.next != tail) {
previous = previous.next;
}
tail = previous;
tail.next = null;
}
currentSize--;
return temp;
}
Here is the second edit with addLast:
public void addLast(E obj){
Node<E> newNode = new Node<E>(obj);
if(head == null) head = tail = newNode;
if(head.next==null){
head.next = tail.next = newNode;
tail = newNode;}
else{
tail.next = newNode;
tail = newNode;}
currentSize++;}