Linked List Entry : Your LinkedList « Collections « Java Tutorial

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2. Collections
3. Your LinkedList

import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

/*
 * Copyright 2005 JBoss Inc
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

public class LinkedListEntry extends AbstractBaseLinkedListNode {

    private static final long serialVersionUID = 400L;
    private Object            object;

    public LinkedListEntry() {
    }

    public LinkedListEntry(final Object object) {
        this.object = object;
    }

    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
        super.readExternal(in);
        object  = in.readObject();
    }

    public void writeExternal(ObjectOutput out) throws IOException {
        super.writeExternal(out);
        out.writeObject(object);
    }
    
    public Object getObject() {
        return this.object;
    }

    public int hashCode() {
        return this.object.hashCode();
    }

    public boolean equals(final Object other) {
        return this.object.equals( other );
    }
}

/**
 * Provides a abstract base implementation that an object can extend so that it can be used in a LinkedList.
 *
 * @see LinkedList
 *
 * @author <a href="mailto:mark.proctor@jboss.com">Mark Proctor</a>
 * @author <a href="mailto:bob@werken.com">Bob McWhirter</a>
 */
 class AbstractBaseLinkedListNode
    implements
    LinkedListNode {

    private static final long serialVersionUID = 400L;

    private LinkedListNode    previous;

    private LinkedListNode    next;

    /**
     * Empty Constructor
     */
    public AbstractBaseLinkedListNode() {
    }

    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
        previous    = (LinkedListNode)in.readObject();
        next    = (LinkedListNode)in.readObject();
    }

    public void writeExternal(ObjectOutput out) throws IOException {
        out.writeObject(previous);
        out.writeObject(next);
    }

    /* (non-Javadoc)
     * @see org.drools.reteoo.LinkedListNode#getNext()
     */
    public LinkedListNode getNext() {
        return this.next;
    }

    /* (non-Javadoc)
     * @see org.drools.reteoo.LinkedListNode#setNext(org.drools.reteoo.LinkedListNode)
     */
    public void setNext(final LinkedListNode next) {
        this.next = next;
    }

    /* (non-Javadoc)
     * @see org.drools.reteoo.LinkedListNode#getPrevious()
     */
    public LinkedListNode getPrevious() {
        return this.previous;
    }

    /* (non-Javadoc)
     * @see org.drools.reteoo.LinkedListNode#setPrevious(org.drools.reteoo.LinkedListNode)
     */
    public void setPrevious(final LinkedListNode previous) {
        this.previous = previous;
    }
}


 /**
  * Items placed in a <code>LinkedList<code> must implement this interface .
  *
  * @see LinkedList
  *
  * @author <a href="mailto:mark.proctor@jboss.com">Mark Proctor</a>
  * @author <a href="mailto:bob@werken.com">Bob McWhirter</a>
  */
  interface LinkedListNode
     extends
     Externalizable {

     /**
      * Returns the next node
      * @return
      *      The next LinkedListNode
      */
     public LinkedListNode getNext();

     /**
      * Sets the next node
      * @param next
      *      The next LinkedListNode
      */
     public void setNext(LinkedListNode next);

     /**
      * Returns the previous node
      * @return
      *      The previous LinkedListNode
      */
     public LinkedListNode getPrevious();

     /**
      * Sets the previous node
      * @param previous
      *      The previous LinkedListNode
      */
     public void setPrevious(LinkedListNode previous);

 }