/*
* Copyright (c) 2001-2007 Sun Microsystems, Inc. All rights reserved.
*
* The Sun Project JXTA(TM) Software License
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. The end-user documentation included with the redistribution, if any, must
* include the following acknowledgment: "This product includes software
* developed by Sun Microsystems, Inc. for JXTA(TM) technology."
* Alternately, this acknowledgment may appear in the software itself, if
* and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must
* not be used to endorse or promote products derived from this software
* without prior written permission. For written permission, please contact
* Project JXTA at http://www.jxta.org.
*
* 5. Products derived from this software may not be called "JXTA", nor may
* "JXTA" appear in their name, without prior written permission of Sun.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SUN
* MICROSYSTEMS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* JXTA is a registered trademark of Sun Microsystems, Inc. in the United
* States and other countries.
*
* Please see the license information page at :
* <http://www.jxta.org/project/www/license.html> for instructions on use of
* the license in source files.
*
* ====================================================================
*
* This software consists of voluntary contributions made by many individuals
* on behalf of Project JXTA. For more information on Project JXTA, please see
* http://www.jxta.org.
*
* This license is based on the BSD license adopted by the Apache Foundation.
*/
package net.jxta.impl.util.ternary;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* Author Wally Flint: wally@wallyflint.com
*
* Lifted from the Java World article: http://www.javaworld.com/javaworld/jw-02-2001/jw-0216-ternary.html
* "With thanks to Michael Amster of webeasy.com for introducing me to the Ternary Search Tree, and providing some starting code."
*
* SimonT: Ensured implementation of Iterator
*/
public class DoublyLinkedList {
private DLLNode head;
private DLLNode last;
private int size = 0;
public void addFirst( Object data ) {
DLLNode newNode = new DLLNode( );
newNode.data = data;
if ( size == 0 ) {
head = newNode;
last = head;
} else {
newNode.nextNode = head;
head.previousNode = newNode;
head = newNode;
}
size++;
}
public void addLast( Object data ) {
DLLNode newNode = new DLLNode( );
newNode.data = data;
if ( size == 0 ) {
head = newNode;
} else {
last.nextNode = newNode;
newNode.previousNode = last;
}
last = newNode;
size++;
}
public void removeFirst( ) {
if ( size <= 1 ) {
head = null;
last = null;
} else {
DLLNode oldHead = head;
head = oldHead.nextNode;
oldHead.nextNode = null;
head.previousNode = null;
}
size--;
}
public void removeLast( ) {
if ( size <= 1 ) {
head = null;
last = null;
} else {
last = last.previousNode;
last.nextNode.previousNode = null;
last.nextNode = null;
}
size--;
}
public int size( ) {
return size;
}
public void clear( ) {
DLLNode currentNode = last;
DLLNode tempNode;
while ( currentNode != null ) {
tempNode = currentNode.previousNode;
currentNode.nextNode = null;
currentNode.previousNode = null;
currentNode.data = null;
currentNode = tempNode;
}
last = null;
head = null;
size = 0;
}
public Iterator<Object> iterator( ) {
return new DLLIterator( );
}
protected class DLLNode {
protected DLLNode nextNode;
protected DLLNode previousNode;
protected Object data;
}
public class DLLIterator implements Iterator<Object> {
private DLLNode currentPreviousNode = null;
private DLLNode currentNextNode = head;
public boolean hasNext( ) {
if ( currentNextNode == null ) {
return false;
} else {
return ( currentNextNode != null );
}
}
public boolean hasPrevious( ) {
if ( currentPreviousNode == null ) {
return false;
} else {
return ( currentPreviousNode != null );
}
}
public Object next( ) {
if ( currentNextNode == null ) {
throw new NoSuchElementException( "Attempt to retrieve next value from " +
"DoublyLinkedList after all values have already been retrieved. Verify hasNext method returns true " +
"before calling next method." );
}
Object data = currentNextNode.data;
DLLNode tempNode = currentNextNode;
currentNextNode = currentNextNode.nextNode;
currentPreviousNode = tempNode;
return data;
}
public Object previous( ) {
if ( currentPreviousNode == null ) {
throw new NoSuchElementException( "Attempt to retrieve previous value from " +
"head node of DoublyLinkedList. Verify hasPrevious method returns true " + "before calling previous method." );
}
Object data = currentPreviousNode.data;
DLLNode tempNode = currentPreviousNode;
currentPreviousNode = currentPreviousNode.previousNode;
currentNextNode = tempNode;
return data;
}
public void resetToBeginning( ) {
currentNextNode = head;
currentPreviousNode = null;
}
public void resetToEnd( ) {
currentNextNode = null;
currentPreviousNode = last;
}
public void remove( ) {
// Not implemented
}
}
}