dxhashmap.java

来自「用Java写的面相对象的数据库管理系统」· Java 代码 · 共 121 行

// 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: DxHashMap.java,v 1.10 2000/11/03 13:56:43 daniela Exp $

package org.ozoneDB.DxLib;

import java.util.Hashtable;
import java.io.Externalizable;


/**
 * A DxMap implementation based on java.util.Hashtable.
 * 
 * @author <a href="http://www.softwarebuero.de/">SMB</a>
 * @version $Revision: 1.10 $Date: 2000/11/03 13:56:43 $
 * 
 * 
 * @author <a href="http://www.softwarebuero.de/">SMB</a>
 * @version $Revision: 1.10 $Date: 2000/11/03 13:56:43 $
 */
public class DxHashMap extends DxAbstractMap implements DxHashCollection {
    
    final static long serialVersionUID = 1L;
    
    protected transient Hashtable ht;
    
    
    public DxHashMap() {
        ht = new Hashtable();
    }
    
    
    public DxHashMap( int size ) {
        ht = new Hashtable( size );
    }
    
    
    public Object clone() {
        DxMap newMap = new DxHashMap( Math.max( count(), 8 ) );
        return clone( newMap );
    } 
    
    
    public boolean addForKey( Object obj, Object key ) {
        synchronized (ht) {
            Object old = ht.put( key, obj );
            if (old != null) {
                ht.put( key, old );
                return false;
            } 
            return true;
        }
    } 
    
    
    public Object elementForKey( Object key ) {
        return ht.get( key );
    } 
    
    
    public Object keyForElement( Object obj ) {
        DxIterator it = iterator();
        Object cursor;
        while ((cursor = it.next()) != null) {
            if (obj.equals( cursor )) {
                return it.key();
            } 
        } 
        return null;
    } 
    
    
    public Object removeForKey( Object key ) {
        return ht.remove( key );
    } 
    
    
    public synchronized boolean remove( Object obj ) {
        Object key = keyForElement( obj );
        if (key != null) {
            removeForKey( key );
            return true;
        } 
        return false;
    } 
    
    
    public int count() {
        return ht.size();
    } 
    
    
    public boolean isEmpty() {
        return ht.isEmpty();
    } 
    
    
    public boolean containsKey( Object key ) {
        return ht.containsKey( key );
    } 
    
    
    public DxIterator iterator() {
        return new DxHashIterator( this );
    } 
    
    
    public void clear() {
        ht.clear();
    } 
    
    
    public Hashtable internalHashtable() {
        return ht;
    } 
}