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MyLinkedList.java
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MyLinkedList.java
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package textgen;
import java.util.AbstractList;
/** A class that implements a doubly linked list
*
* @author UC San Diego Intermediate Programming MOOC team
*
* @param <E> The type of the elements stored in the list
*/
public class MyLinkedList<E> extends AbstractList<E> {
LLNode<E> head;
LLNode<E> tail;
int size;
/** Create a new empty LinkedList */
public MyLinkedList() {
size = 0;
head = null;
tail = null;
}
/**
* Appends an element to the end of the list
* @param element The element to add
* @return
*/
public boolean add(E element )
{
if(element != null) {
LLNode<E> node = new LLNode<E>(element);
if (head == null) {
head = node;
tail = node;
head.next = null;
tail.prev = null;
}
else {
tail.next = node;
node.prev = tail;
tail = node;
}
size++;
return true;
}
else {
throw new NullPointerException();
}
}
/** Get the element at position index
* @throws IndexOutOfBoundsException if the index is out of bounds. */
public E get(int index)
{
if (index >=0 && index < size) {
LLNode<E> node = head;
for(int i = index; i > 0; i--) {
node = node.next;
}
return node.data;
}
else {
throw new IndexOutOfBoundsException();
}
}
/**
* Add an element to the list at the specified index
* @param The index where the element should be added
* @param element The element to add
*/
public void add(int index, E element )
{
if (element != null) {
LLNode<E> node = new LLNode<E>(element);
if (index >= 0 && index <= size) {
if(size == 0) {
head = node;
tail = node;
}
else {
if (index == 0) {
head.prev = node;
node.next = head;
head = node;
}
else if (index == size) {
tail.next = node;
node.prev = tail;
tail = node;
}
else {
LLNode<E> node_tmp = head;
for (int i = index; i > 0; i--) {
node_tmp = node_tmp.next;
}
node.next = node_tmp;
node.prev = node_tmp.prev;
node_tmp.prev.next = node;
node_tmp.prev = node;
}
}
size++;
}
else {
throw new IndexOutOfBoundsException();
}
}
else {
throw new NullPointerException();
}
}
/** Return the size of the list */
public int size()
{
return size;
}
/** Remove a node at the specified index and return its data element.
* @param index The index of the element to remove
* @return The data element removed
* @throws IndexOutOfBoundsException If index is outside the bounds of the list
*
*/
public E remove (int index)
{
if (size == 1) {
if (index == 0) {
E out;
out = head.data;
head = null;
size--;
return out;
}
else {
throw new IndexOutOfBoundsException();
}
}
if (size > 1) {
if (index >= 0 && index < size) {
E out;
if (index == 0) {
out = head.data;
head = head.next;
head.prev = null;
}
else if (index == size - 1) {
out = tail.data;
tail = tail.prev;
tail.next = null;
}
else {
LLNode<E> node = head;
for (int i = index; i > 0; i--) {
node = node.next;
}
out = node.data;
node.prev.next = node.next;
node.next.prev = node.prev;
}
size--;
return out;
}
else {
throw new IndexOutOfBoundsException();
}
}
else {
throw new NullPointerException();
}
}
/**
* Set an index position in the list to a new element
* @param index The index of the element to change
* @param element The new element
* @return The element that was replaced
* @throws IndexOutOfBoundsException if the index is out of bounds.
*/
public E set(int index, E element)
{
if (element != null) {
if (index >=0 && index < size) {
LLNode<E> node = head;
for(int i = index; i > 0; i--) {
node = node.next;
}
E out = node.data;
node.data = element;
return out;
}
else {
throw new IndexOutOfBoundsException();
}
}
else {
throw new NullPointerException();
}
}
}
class LLNode<E>
{
LLNode<E> prev;
LLNode<E> next;
E data;
// Add any other methods you think are useful here
// E.g. you might want to add another constructor
public LLNode(E e)
{
this.data = e;
this.prev = null;
this.next = null;
}
}