1 public class LinkedListElement {
2 public LinkedListElement next;
3 public LinkedListElement prev;
6 public LinkedListElement( Object e,
8 LinkedListElement p ) {
15 public class LinkedList {
16 LinkedListElement head;
17 LinkedListElement tail;
24 public add( Object o ) {
26 head = new LinkedListElement( o, null, null );
30 tail.next = new LinkedListElement( o, null, tail );
36 public addFirst( Object o ) {
38 head = new LinkedListElement( o, null, null );
42 head.prev = new LinkedListElement( o, head, null );
48 public addLast( Object o ) {
62 public boolean isEmpty() {
66 public Object clone() {
67 System.out.println( "LinkedList.clone() not implemented." );
71 public boolean contains( Object o ) {
72 LinkedListElement e = head;
74 if( e.element == o ) {
82 public Object getFirst() {
89 public Object getLast() {
96 public Object element() {
100 public Object peek() {
104 public Object peekFirst() {
108 public Object peekLast() {
112 public Object removeFirst() {
114 System.out.println( "LinkedList: illegal removeFirst()" );
117 Object o = head.element;
128 public Object removeLast() {
130 System.out.println( "LinkedList: illegal removeLast()" );
133 Object o = tail.element;
144 public void remove( Object o ) {
146 System.out.println( "LinkedList: illegal remove( Object o )" );
149 LinkedListElement e = head;
151 if( e.element == o ) {
152 if( e.prev != null ) {
153 e.prev.next = e.next;
155 if( e.next != null ) {
156 e.next.prev = e.prev;
163 System.out.println( "LinkedList: illegal remove( Object o ), "+o+" not found" );
167 public Object pop() {
168 Object o = getFirst();
173 public void push( Object o ) {
177 public Iterator iterator() {
178 return new LinkedListIterator( this );
182 public class LinkedListIterator extends Iterator {
184 LinkedListElement itr;
187 public LinkedListIterator( LinkedList ll ) {
193 public boolean hasNext() {
197 public Object next() {
199 System.out.println( "LinkedListIterator: illegal next()" );
202 removeable = itr.element;
207 public void remove() {
208 if( removeable == null ) {
209 System.out.println( "LinkedListIterator: illegal remove()" );
212 ll.remove( removeable );