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 Object clone() {
63 System.out.println( "LinkedList.clone() not implemented." );
67 public boolean contains( Object o ) {
68 LinkedListElement e = head;
70 if( e.element == o ) {
78 public Object getFirst() {
85 public Object getLast() {
92 public Object element() {
96 public Object peek() {
100 public Object peekFirst() {
104 public Object peekLast() {
108 public void removeFirst() {
110 System.out.println( "LinkedList: illegal removeFirst()" );
122 public void removeLast() {
124 System.out.println( "LinkedList: illegal removeLast()" );
136 public void remove( Object o ) {
138 System.out.println( "LinkedList: illegal remove( Object o )" );
141 LinkedListElement e = head;
143 if( e.element == o ) {
144 if( e.prev != null ) {
145 e.prev.next = e.next;
147 if( e.next != null ) {
148 e.next.prev = e.prev;
155 System.out.println( "LinkedList: illegal remove( Object o ), "+o+" not found" );
159 public Object pop() {
160 Object o = getFirst();
165 public void push( Object o ) {
169 public Iterator iterator() {
170 return new LinkedListIterator( this );
174 public class LinkedListIterator extends Iterator {
176 LinkedListElement itr;
179 public LinkedListIterator( LinkedList ll ) {
185 public boolean hasNext() {
189 public Object next() {
191 System.out.println( "LinkedListIterator: illegal next()" );
194 removeable = itr.element;
199 public void remove() {
200 if( removeable == null ) {
201 System.out.println( "LinkedListIterator: illegal remove()" );
204 ll.remove( removeable );