Linked List help

[auhunter]

Hello, I'm wanting to make sure I'm doing this correctly. I'm attempting to turn the below code for a single linked list into a double linked list. The first one is the code we are given, and the 2nd is the modifications I've made to it thus far. Am I doing it correctly? Also, any advice for how to turn the single linked list into a circular linked list would also be very beneficial.

public class MyLinkedList<E> extends MyAbstractList<E> {

private Node<E> head, tail;



/** Create a default list */

public MyLinkedList() {

}



/** Create a list from an array of objects */

public MyLinkedList(E[] objects) {

super(objects);

}



/** Return the head element in the list */

public E getFirst() {

if (size == 0) {

return null;

}

else {

return head.element;

}

}



/** Return the last element in the list */

public E getLast() {

if (size == 0) {

return null;

}

else {

return tail.element;

}

}



/** Add an element to the beginning of the list */

public void addFirst(E e) {

Node<E> newNode = new Node<E>(e); // Create a new node
newNode.next = head; // link the new node with the head
head = newNode; // head points to the new node
size++; // Increase list size


if (tail == null) // the new node is the only node in list
tail = head;

}



/** Add an element to the end of the list */

public void addLast(E e) {

Node<E> newNode = new Node<E>(e); // Create a new for element e


if (tail == null) {

head = tail = newNode; // The new node is the only node in list
}

else {

tail.next = newNode; // Link the new with the last node
tail = tail.next; // tail now points to the last node
}



size++; // Increase size
}





/** Add a new element at the specified index in this list
* The index of the head element is 0 */

public void add(int index, E e) {

if (index == 0) {

addFirst(e);

}

else if (index >= size) {

addLast(e);

}

else {

Node<E> current = head;

for (int i = 1; i < index; i++) {

current = current.next;

}

Node<E> temp = current.next;

current.next = new Node<E>(e);

(current.next).next = temp;

size++;

}

}



/** Remove the head node and
* return the object that is contained in the removed node. */

public E removeFirst() {

if (size == 0) {

return null;

}

else {

Node<E> temp = head;

head = head.next;

size--;

if (head == null) {

tail = null;

}

return temp.element;

}

}



/** Remove the last node and
* return the object that is contained in the removed node. */

public E removeLast() {

if (size == 0) {

return null;

}

else if (size == 1) {

Node<E> temp = head;

head = tail = null;

size = 0;

return temp.element;

}

else {

Node<E> current = head;



for (int i = 0; i < size - 2; i++) {

current = current.next;

}



Node<E> temp = tail;

tail = current;

tail.next = null;

size--;

return temp.element;

}

}



/** Remove the element at the specified position in this list.
* Return the element that was removed from the list. */

public E remove(int index) {

if (index < 0 || index >= size) {

return null;

}

else if (index == 0) {

return removeFirst();

}

else if (index == size - 1) {

return removeLast();

}

else {

Node<E> previous = head;



for (int i = 1; i < index; i++) {

previous = previous.next;

}



Node<E> current = previous.next;

previous.next = current.next;

size--;

return current.element;

}

}



/** Override toString() to return elements in the list */

public String toString() {

StringBuilder result = new StringBuilder("[");



Node<E> current = head;

for (int i = 0; i < size; i++) {

result.append(current.element);

current = current.next;

if (current != null) {

result.append(", "); // Separate two elements with a comma
}

else {

result.append("]"); // Insert the closing ] in the string
}

}



return result.toString();

}



/** Clear the list */

public void clear() {

head = tail = null;

}



/** Return true if this list contains the element o */

public boolean contains(E e) {

System.out.println("Implementation left as an exercise");

return true;

}



/** Return the element from this list at the specified index */

public E get(int index) {
Node<E> temp = head;
for(int i = 0; i<index;i++){
temp = temp.next;
}

//System.out.println("Implementation left as an exercise");
return temp.element;

}

public E getFromEnd(int index){
return get(size()-index);
}



/** Return the index of the head matching element in this list.
* Return -1 if no match. */

public int indexOf(E e) {

System.out.println("Implementation left as an exercise");

return 0;

}



/** Return the index of the last matching element in this list
* Return -1 if no match. */

public int lastIndexOf(E e) {

System.out.println("Implementation left as an exercise");

return 0;

}



/** Replace the element at the specified position in this list
* with the specified element. */

public E set(int index, E e) {

System.out.println("Implementation left as an exercise");

return null;

}



private static class Node<E> {

E element;

Node<E> next;



public Node(E element) {

this.element = element;

}

}

}

public class MyDoubleLinkedList<E> extends MyAbstractList<E> {

private Node<E> head, tail;



/** Create a default list */

public MyDoubleLinkedList() {

}



/** Create a list from an array of objects */

public MyDoubleLinkedList(E[] objects) {

super(objects);

}



/** Return the head element in the list */

public E getFirst() {

if (size == 0) {

return null;

}

else {

return head.element;

}

}



/** Return the last element in the list */

public E getLast() {

if (size == 0) {

return null;

}

else {

return tail.element;

}

}



/** Add an element to the beginning of the list */

public void addFirst(E e) {

Node<E> newNode = new Node<E>(e); // Create a new node
newNode.next = head; // link the new node with the head
head = newNode; // head points to the new node
head.next.previous = head;
size++; // Increase list size


if (tail == null) // the new node is the only node in list
tail = head;

}



/** Add an element to the end of the list */

public void addLast(E e) {

Node<E> newNode = new Node<E>(e); // Create a new for element e

if (tail == null) {

head = tail = newNode; // The new node is the only node in list
}

else {

tail.next = newNode; // Link the new with the last node
tail.next.previous = tail;
tail = tail.next; // tail now points to the last node
}



size++; // Increase size
}





/** Add a new element at the specified index in this list
* The index of the head element is 0 */

public void add(int index, E e) {

if (index == 0) {

addFirst(e);

}

else if (index >= size) {

addLast(e);

}

else {

Node<E> current = head;

for (int i = 1; i < index; i++) {

current = current.next;

}

Node<E> temp = current.next;

current.next = new Node<E>(e);

current.next.previous = current;

(current.next).next = temp;

temp.previous = current.next;

size++;

}

}



/** Remove the head node and
* return the object that is contained in the removed node. */

public E removeFirst() {

if (size == 0) {

return null;

}

else {

Node<E> temp = head;

head = head.next;

head.previous = null;

size--;

if (head == null) {

tail = null;

}

return temp.element;

}

}



/** Remove the last node and
* return the object that is contained in the removed node. */

public E removeLast() {

if (size == 0) {

return null;

}

else if (size == 1) {

Node<E> temp = head;

head = tail = null;

size = 0;

return temp.element;

}

else {

Node<E> current = head;



for (int i = 0; i < size - 2; i++) {

current = current.next;

}



Node<E> temp = tail;

tail = current;

tail.next = null;

size--;

return temp.element;

}

}



/** Remove the element at the specified position in this list.
* Return the element that was removed from the list. */

public E remove(int index) {

if (index < 0 || index >= size) {

return null;

}

else if (index == 0) {

return removeFirst();

}

else if (index == size - 1) {

return removeLast();

}

else {

Node<E> previous = head;



for (int i = 1; i < index; i++) {

previous = previous.next;

}



Node<E> current = previous.next;

previous.next = current.next;

current.next.previous = previous;

size--;

return current.element;

}

}



/** Override toString() to return elements in the list */

public String toString() {

StringBuilder result = new StringBuilder("[");



Node<E> current = head;

for (int i = 0; i < size; i++) {

result.append(current.element);

current = current.next;

if (current != null) {

result.append(", "); // Separate two elements with a comma
}

else {

result.append("]"); // Insert the closing ] in the string
}

}



return result.toString();

}



/** Clear the list */

public void clear() {

head = tail = null;

}



/** Return true if this list contains the element o */

public boolean contains(E e) {

System.out.println("Implementation left as an exercise");

return true;

}



/** Return the element from this list at the specified index */

public E get(int index) {
Node<E> temp = head;
for(int i = 0; i<index;i++){
temp = temp.next;
}

//System.out.println("Implementation left as an exercise");
return temp.element;

}

public E getFromEnd(int index){
return get(size()-index);
}



/** Return the index of the head matching element in this list.
* Return -1 if no match. */

public int indexOf(E e) {

System.out.println("Implementation left as an exercise");

return 0;

}



/** Return the index of the last matching element in this list
* Return -1 if no match. */

public int lastIndexOf(E e) {

System.out.println("Implementation left as an exercise");

return 0;

}



/** Replace the element at the specified position in this list
* with the specified element. */

public E set(int index, E e) {

System.out.println("Implementation left as an exercise");

return null;

}



private static class Node<E> {

E element;

Node<E> next, previous;



public Node(E element) {

this.element = element;

}

}

}

[DarrylBurke]

Not enough code. I printed it out on rice paper, fried and ate it and I'm still hungry.

db

-- Read How to ask questions the smart way

[auhunter]

What more are you looking for? The class it's extending?