/**
* Returns a string representation of the contents of the linked list, from the front to the back.
*
* @return a string representation of the linked list, from front to back
*/
public String toString() {
if (isEmpty()) {
return "";
} else if (getHead() == getTail()) {
// one element
return getHead().getElement().toString();
} else {
StringBuilder newString = new StringBuilder();
DLNode<T> placeHolder = getHead();
// loop through and build string node by node
while (placeHolder.getNext() != null) {
newString.append(placeHolder.getElement().toString());
placeHolder = placeHolder.getNext();
}
newString.append(placeHolder.getElement().toString());
return newString.toString();
}
}
/**
* Remove and return the element at the back of the linked list.
*
* @return the element that was at the back of the linked list
* @throws NoSuchElementException if attempting to remove from an empty list
*/
public T removeFromBack() {
if (isEmpty()) {
throw new NoSuchElementException();
}
DLNode<T> oldTail = getTail();
if (getTail().getPrevious() != null) {
// fix next for new tail and set new tail
getTail().getPrevious().setNext(null);
setTail(getTail().getPrevious());
} else {
// removed last node
setTail(null);
setHead(null);
}
return oldTail.getElement();
}
/**
* Remove and return the element at the front of the linked list.
*
* @return the element that was at the front of the linked list
* @throws NoSuchElementException if attempting to remove from an empty list
*/
public T removeFromFront() {
if (isEmpty()) {
throw new NoSuchElementException();
}
DLNode<T> oldHead = getHead();
if (getHead().getNext() != null) {
// fix previous for new head and set new head
getHead().getNext().setPrevious(null);
setHead(getHead().getNext());
} else {
// removed last node
setHead(null);
setTail(null);
}
return oldHead.getElement();
}