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package ca.ubc.cs.spl.aspectPatterns.patternLibrary;
/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* This file is part of the design patterns project at UBC
*
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* either https://www.mozilla.org/MPL/ or https://aspectj.org/MPL/.
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is ca.ubc.cs.spl.aspectPatterns.
*
* For more details and the latest version of this code, please see:
* https://www.cs.ubc.ca/labs/spl/projects/aodps.html
*
* Contributor(s):
*/
import java.util.Hashtable;
/**
* Implements a the abstracted Flyweight design pattern. Included is the
* general creation-on-demand logic. Concrete subaspects are used to
* defines the actual <i>FlyweightFactories</i>.
*
* Concrete subaspects need only to assign the flyweight roles and to
* overwrite the <code>createFlyweight(Object)<code> method.
*
* @author Jan Hannemann
* @author Gregor Kiczales
* @version 1.1, 02/11/04
*/
public abstract aspect FlyweightProtocol {
/**
* stores the existing <i>Flyweight</i> by key
*/
private Hashtable flyweights = new Hashtable();
/**
* defines the <i>Flyweight</i> role.
*/
protected interface Flyweight{};
/**
* Creates a <i>Flyweight</i> for a given key. This method is called by
* <code>getFlyweight(Object)</code> if the flyweight does not already
* exist.
*
* @param key the key identifying the particular flyweight
* @return the <i>Flyweight</i> representing the key
*/
protected abstract Flyweight createFlyweight(Object key);
/**
* Returns the <i>Flyweight</i> for a particular key.
* If the appropriate <i>Flyweight</i> does not yet exist, it is created
* on demand.
*
* @param key the key identifying the particular <i>Flyweight</i>
* @return the <i>Flyweight</i> representing the key
*/
public Flyweight getFlyweight(Object key) {
if (flyweights.containsKey(key)) {
return (Flyweight) flyweights.get(key);
} else {
Flyweight flyweight = createFlyweight(key);
flyweights.put(key, flyweight);
return flyweight;
}
}
}
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