dxlistbag.java

用Java写的面相对象的数据库管理系统

// You can redistribute this software and/or modify it under the terms of
// the Ozone Library License version 1 published by ozone-db.org.
//
// The original code and portions created by SMB are
// Copyright (C) 1997-2000 by SMB GmbH. All rights reserved.
//
// $Id: DxListBag.java,v 1.6 2000/10/28 16:55:14 daniela Exp $

package org.ozoneDB.DxLib;


public class DxListBag extends DxAbstractBag implements DxListCollection {
    
    final static long serialVersionUID = 1L;
    
    protected transient DxListNode start;
    protected transient DxListNode top;
    protected transient int itemCount = 0;
    
    
    /**
     */
    public DxListBag() {
        start = new DxListNode();
        top = new DxListNode();
        start.storeBehind( top );
    }
    
    
    /**
     */
    public synchronized boolean add( Object obj ) {
        return addBack( obj );
    } 
    
    
    /**
     */
    public synchronized boolean addFront( Object obj ) {
        DxListNode node = new DxListNode( obj );
        start.storeBehind( node );
        itemCount++;
        return true;
    } 
    
    
    /**
     */
    public synchronized boolean addBack( Object obj ) {
        DxListNode node = new DxListNode( obj );
        top.storeInfront( node );
        itemCount++;
        return true;
    } 
    
    
    /**
     */
    public DxIterator iterator() {
        return new DxListIterator( this );
    } 
    
    
    /**
     */
    public int count() {
        return itemCount;
    } 
    
    
    /**
     */
    public boolean isEmpty() {
        return start.next() == top;
    } 
    
    
    /**
     */
    public synchronized void clear() {
        start = new DxListNode();
        top = new DxListNode();
        start.storeBehind( top );
        itemCount = 0;
    } 
    
    
    /**
     */
    public DxListNode head() {
        return start;
    } 
    
    
    /**
     */
    public DxListNode tail() {
        return top;
    } 
    
    
    /**
     */
    public void decCounter() {
        itemCount--;
    } 
    
}