dxvectoriterator.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: DxVectorIterator.java,v 1.7 2000/10/28 16:55:14 daniela Exp $

package org.ozoneDB.DxLib;

import java.io.*;
import java.util.*;

/**
 * 
 * 
 * @author <a href="http://www.softwarebuero.de/">SMB</a>
 * @version $Revision: 1.7 $Date: 2000/10/28 16:55:14 $
 */
public final class DxVectorIterator extends DxAbstractIterator {
    
    final static long serialVersionUID = 1L;
    
    DxVectorCollection coll;
    Vector vector;
    int currentIndex;
    Object currentObject;
    
    
    /**
     */
    public DxVectorIterator( DxVectorCollection _coll ) {
        coll = _coll;
        vector = coll.internalVector();
        reset();
    }
    
    
    /**
     */
    public Object object() {
        return currentObject;
    } 
    
    
    /**
     */
    public Object next() {
        if (atFirstObject) {
            atFirstObject = false;
        } else {
            try {
                //skip null elements
                while ((currentObject = vector.elementAt( ++currentIndex )) == null);
            } catch (ArrayIndexOutOfBoundsException e) {
                //object returns null if currentIndex exceeds vector size
                currentObject = null;
            } 
        } 
        return currentObject;
    } 
    
    
    /**
     */
    public void reset() {
        atFirstObject = true;
        objectRemoved = false;
        currentIndex = 0;
        currentObject = currentIndex < vector.size() ? vector.elementAt( currentIndex ) : null;
    } 
    
    
    /**
     */
    public synchronized Object removeObject() {
        Object answer = vector.elementAt( currentIndex );
        //decrement index to point to the same index after next()
        vector.removeElementAt( currentIndex-- );
        return answer;
    } 
}