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wcrisman
221
Foundation/src/com/foundation/util/ObservableAggregator.java
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Foundation/src/com/foundation/util/ObservableAggregator.java
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/*
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* Copyright (c) 2006,2008 Declarative Engineering LLC.
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* All rights reserved. This program and the accompanying materials
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* are made available under the terms of the Declarative Engineering LLC
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* verson 1 which accompanies this distribution, and is available at
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* http://declarativeengineering.com/legal/DE_Developer_License_v1.txt
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*/
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package com.foundation.util;
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import com.common.thread.Monitor;
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import com.common.thread.ThreadService;
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import com.common.util.ICollection;
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import com.common.util.LiteHashMap;
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import com.common.util.LiteList;
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import com.foundation.util.Updater.UpdaterRunnable;
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/**
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* This base class provides functionality for aggregators of zero or more observable collections.
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*/
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public abstract class ObservableAggregator {
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/** The number of times the startChanges() method has been called. This allows multiple threads to notify this aggregator of changes at the same time. */
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protected int changeStartCounter = 0;
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/** The set of listeners indexed by the collection they are listening to. */
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private LiteHashMap listenersByCollectionMap = new LiteHashMap(10);
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/**
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* An instance of Listener should be created for each collection being listened to - each collection that makes up the aggregate collection.
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*/
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private class Listener implements IInlineCollectionObserver {
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/** The collection being listened to. */
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private IInlineCollectionObservable collection = null;
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/** A collection used to temporarily collect items being added to the aggregate collection. */
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protected LiteList addedItems = null;
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/** A collection used to temporarily collect items being removed from the aggregate collection. */
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protected LiteList removedItems = null;
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/**
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* Listener constructor.
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* @param collection The collection being listened to.
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*/
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public Listener(IInlineCollectionObservable collection) {
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this.collection = collection;
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}//Listener()//
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/* (non-Javadoc)
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* @see com.foundation.util.IInlineCollectionObserver#removingAll()
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*/
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public void removingAll() {
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removedItems.addAll(collection.getCollection());
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}//removingAll()//
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/* (non-Javadoc)
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* @see com.foundation.util.IInlineCollectionObserver#valueAdded(java.lang.Object)
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*/
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public void valueAdded(Object value) {
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if(addedItems != null) {
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addedItems.add(value);
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}//if//
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else {
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final Object added = value;
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applyChange(new Runnable() {
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public void run() {
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applyAddChange(added);
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}//run()//
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});
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}//else//
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}//valueAdded()//
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/* (non-Javadoc)
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* @see com.foundation.util.IInlineCollectionObserver#valueRemoved(java.lang.Object)
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*/
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public void valueRemoved(Object value) {
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if(removedItems != null) {
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removedItems.add(value);
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}//if//
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else {
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final Object removed = value;
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applyChange(new Runnable() {
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public void run() {
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applyRemoveChange(removed);
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}//run()//
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});
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}//else//
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}//valueRemoved()//
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/* (non-Javadoc)
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* @see com.foundation.util.IInlineCollectionObserver#startChanges(int)
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*/
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public void startChanges(int changeCount) {
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changeStartCounter++;
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addedItems = new LiteList(changeCount);
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removedItems = new LiteList(changeCount);
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}//startChanges()//
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/* (non-Javadoc)
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* @see com.foundation.util.IInlineCollectionObserver#stopChanges()
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*/
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public void stopChanges() {
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if(--changeStartCounter == 0) {
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final LiteList addedItems = this.addedItems;
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final LiteList removedItems = this.removedItems;
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this.addedItems = null;
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this.removedItems = null;
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//Apply the changes.//
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applyChange(new Runnable() {
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public void run() {
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applyChanges(addedItems, removedItems);
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}//run()//
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});
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}//if//
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}//stopChanges()//
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}//Listener//
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/**
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* ObservableAggregator constructor.
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*/
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public ObservableAggregator() {
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super();
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}//ObservableAggregator()//
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/**
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* Releases the aggregator and stops all listeners.
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* <p>Warning: Failure to call this method may result in memory leaks and wasted cycles.</p>
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*/
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public void release() {
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IInlineCollectionObservable[] collections = new IInlineCollectionObservable[listenersByCollectionMap.getSize()];
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listenersByCollectionMap.toKeyArray(collections);
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for(int index = 0; index < collections.length; index++) {
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removeCollection(collections[index]);
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}//for//
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}//release()//
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/**
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* Adds the collection to this aggregator.
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* @param collection The collection to be added.
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*/
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public void addCollection(IInlineCollectionObservable collection) {
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Monitor monitor = collection.getMonitor();
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Monitor.lock(monitor);
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try {
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if(listenersByCollectionMap.containsKey(collection)) {
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//Cannot add a collection twice.//
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throw new IllegalArgumentException();
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}//if//
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Listener listener = new Listener(collection);
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collection.addCollectionObserver(listener);
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listenersByCollectionMap.put(collection, listener);
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}//try//
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finally {
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Monitor.unlock(monitor);
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}//finally//
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}//addCollection()//
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/**
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* Removes the collection from this aggregator.
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* @param collection The collection to be removed.
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*/
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public void removeCollection(IInlineCollectionObservable collection) {
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Monitor monitor = collection.getMonitor();
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Monitor.lock(monitor);
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try {
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Listener listener = (Listener) listenersByCollectionMap.get(collection);
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if(listener != null) {
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collection.removeCollectionObserver(listener);
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}//if//
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else {
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//Cannot remove a collection not previously added.//
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throw new IllegalArgumentException();
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}//else//
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}//try//
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finally {
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Monitor.unlock(monitor);
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}//finally//
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}//removeCollection()//
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/**
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* Applies the changes represented by the runnable that will enact the changes.
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* @param runnable The object run to apply the changes.
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*/
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private void applyChange(final Runnable runnable) {
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if(getAggregateMonitor() != null && !ThreadService.getIsSingleThreadedContext()) {
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Updater.getSingleton().run(new UpdaterRunnable() {
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public void run() {
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runnable.run();
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}//run()//
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public Monitor getMonitor() {
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return getAggregateMonitor();
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}//getMonitor()//
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});
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}//if//
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else {
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runnable.run();
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}//else//
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}//applyChange()//
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/**
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* Gets the monitor for the aggregate.
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* @return The monitor used to lock the aggregate collection as changes get applied.
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*/
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protected abstract Monitor getAggregateMonitor();
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/**
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* Requests that the added and removed items are applied to the aggregate collection.
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* The caller will have already locked on the aggregate's monitor.
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* @param addedItems The items to be added.
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* @param removedItems The items to be removed.
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*/
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protected abstract void applyChanges(ICollection addedItems, ICollection removedItems);
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/**
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* Requests that the item be added to the aggregate collection.
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* The caller will have already locked on the aggregate's monitor.
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* @param item The item to be added.
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*/
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protected abstract void applyAddChange(Object item);
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/**
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* Requests that the item be removed from the aggregate collection.
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* The caller will have already locked on the aggregate's monitor.
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* @param item The item to be removed.
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*/
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protected abstract void applyRemoveChange(Object item);
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}//ObservableAggregator//
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