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/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.commons.collections4.collection; import java.io.Serializable; import java.lang.reflect.Array; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.Iterator; import java.util.List; import org.apache.commons.collections4.iterators.EmptyIterator; import org.apache.commons.collections4.iterators.IteratorChain; import org.apache.commons.collections4.list.UnmodifiableList; /** * Decorates a collection of other collections to provide a single unified view. * <p> * Changes made to this collection will actually be made on the decorated collection. * Add and remove operations require the use of a pluggable strategy. If no * strategy is provided then add and remove are unsupported. * * @param <E> the type of the elements in the collection * @since 3.0 * @version $Id: CompositeCollection.java 1543268 2013-11-19 00:49:59Z ggregory $ */ public class CompositeCollection<E> implements Collection<E>, Serializable { /** Serialization version */ private static final long serialVersionUID = 8417515734108306801L; /** CollectionMutator to handle changes to the collection */ private CollectionMutator<E> mutator; /** Collections in the composite */ private final List<Collection<E>> all = new ArrayList<Collection<E>>(); /** * Create an empty CompositeCollection. */ public CompositeCollection() { super(); } /** * Create a Composite Collection with one collection. * * @param compositeCollection the Collection to be appended to the composite */ public CompositeCollection(final Collection<E> compositeCollection) { super(); addComposited(compositeCollection); } /** * Create a Composite Collection with two collections. * * @param compositeCollection1 the Collection to be appended to the composite * @param compositeCollection2 the Collection to be appended to the composite */ public CompositeCollection(final Collection<E> compositeCollection1, final Collection<E> compositeCollection2) { super(); addComposited(compositeCollection1, compositeCollection2); } /** * Create a Composite Collection with an array of collections. * * @param compositeCollections the collections to composite */ public CompositeCollection(final Collection<E>... compositeCollections) { super(); addComposited(compositeCollections); } //----------------------------------------------------------------------- /** * Gets the size of this composite collection. * <p> * This implementation calls <code>size()</code> on each collection. * * @return total number of elements in all contained containers */ public int size() { int size = 0; for (final Collection<E> item : all) { size += item.size(); } return size; } /** * Checks whether this composite collection is empty. * <p> * This implementation calls <code>isEmpty()</code> on each collection. * * @return true if all of the contained collections are empty */ public boolean isEmpty() { for (final Collection<E> item : all) { if (item.isEmpty() == false) { return false; } } return true; } /** * Checks whether this composite collection contains the object. * <p> * This implementation calls <code>contains()</code> on each collection. * * @param obj the object to search for * @return true if obj is contained in any of the contained collections */ public boolean contains(final Object obj) { for (final Collection<E> item : all) { if (item.contains(obj)) { return true; } } return false; } /** * Gets an iterator over all the collections in this composite. * <p> * This implementation uses an <code>IteratorChain</code>. * * @return an <code>IteratorChain</code> instance which supports * <code>remove()</code>. Iteration occurs over contained collections in * the order they were added, but this behavior should not be relied upon. * @see IteratorChain */ public Iterator<E> iterator() { if (all.isEmpty()) { return EmptyIterator.<E>emptyIterator(); } final IteratorChain<E> chain = new IteratorChain<E>(); for (final Collection<E> item : all) { chain.addIterator(item.iterator()); } return chain; } /** * Returns an array containing all of the elements in this composite. * * @return an object array of all the elements in the collection */ public Object[] toArray() { final Object[] result = new Object[size()]; int i = 0; for (final Iterator<E> it = iterator(); it.hasNext(); i++) { result[i] = it.next(); } return result; } /** * Returns an object array, populating the supplied array if possible. * See <code>Collection</code> interface for full details. * * @param <T> the type of the elements in the collection * @param array the array to use, populating if possible * @return an array of all the elements in the collection */ @SuppressWarnings("unchecked") public <T> T[] toArray(final T[] array) { final int size = size(); Object[] result = null; if (array.length >= size) { result = array; } else { result = (Object[]) Array.newInstance(array.getClass().getComponentType(), size); } int offset = 0; for (final Collection<E> item : all) { for (final E e : item) { result[offset++] = e; } } if (result.length > size) { result[size] = null; } return (T[]) result; } /** * Adds an object to the collection, throwing UnsupportedOperationException * unless a CollectionMutator strategy is specified. * * @param obj the object to add * @return {@code true} if the collection was modified * @throws UnsupportedOperationException if CollectionMutator hasn't been set * @throws UnsupportedOperationException if add is unsupported * @throws ClassCastException if the object cannot be added due to its type * @throws NullPointerException if the object cannot be added because its null * @throws IllegalArgumentException if the object cannot be added */ public boolean add(final E obj) { if (mutator == null) { throw new UnsupportedOperationException( "add() is not supported on CompositeCollection without a CollectionMutator strategy"); } return mutator.add(this, all, obj); } /** * Removes an object from the collection, throwing UnsupportedOperationException * unless a CollectionMutator strategy is specified. * * @param obj the object being removed * @return true if the collection is changed * @throws UnsupportedOperationException if removed is unsupported * @throws ClassCastException if the object cannot be removed due to its type * @throws NullPointerException if the object cannot be removed because its null * @throws IllegalArgumentException if the object cannot be removed */ public boolean remove(final Object obj) { if (mutator == null) { throw new UnsupportedOperationException( "remove() is not supported on CompositeCollection without a CollectionMutator strategy"); } return mutator.remove(this, all, obj); } /** * Checks whether this composite contains all the elements in the specified collection. * <p> * This implementation calls <code>contains()</code> for each element in the * specified collection. * * @param coll the collection to check for * @return true if all elements contained */ public boolean containsAll(final Collection<?> coll) { for (final Object item : coll) { if (contains(item) == false) { return false; } } return true; } /** * Adds a collection of elements to this collection, throwing * UnsupportedOperationException unless a CollectionMutator strategy is specified. * * @param coll the collection to add * @return true if the collection was modified * @throws UnsupportedOperationException if CollectionMutator hasn't been set * @throws UnsupportedOperationException if add is unsupported * @throws ClassCastException if the object cannot be added due to its type * @throws NullPointerException if the object cannot be added because its null * @throws IllegalArgumentException if the object cannot be added */ public boolean addAll(final Collection<? extends E> coll) { if (mutator == null) { throw new UnsupportedOperationException( "addAll() is not supported on CompositeCollection without a CollectionMutator strategy"); } return mutator.addAll(this, all, coll); } /** * Removes the elements in the specified collection from this composite collection. * <p> * This implementation calls <code>removeAll</code> on each collection. * * @param coll the collection to remove * @return true if the collection was modified * @throws UnsupportedOperationException if removeAll is unsupported */ public boolean removeAll(final Collection<?> coll) { if (coll.size() == 0) { return false; } boolean changed = false; for (final Collection<E> item : all) { changed |= item.removeAll(coll); } return changed; } /** * Retains all the elements in the specified collection in this composite collection, * removing all others. * <p> * This implementation calls <code>retainAll()</code> on each collection. * * @param coll the collection to remove * @return true if the collection was modified * @throws UnsupportedOperationException if retainAll is unsupported */ public boolean retainAll(final Collection<?> coll) { boolean changed = false; for (final Collection<E> item : all) { changed |= item.retainAll(coll); } return changed; } /** * Removes all of the elements from this collection . * <p> * This implementation calls <code>clear()</code> on each collection. * * @throws UnsupportedOperationException if clear is unsupported */ public void clear() { for (final Collection<E> coll : all) { coll.clear(); } } //----------------------------------------------------------------------- /** * Specify a CollectionMutator strategy instance to handle changes. * * @param mutator the mutator to use */ public void setMutator(final CollectionMutator<E> mutator) { this.mutator = mutator; } /** * Add these Collections to the list of collections in this composite * * @param compositeCollection the Collection to be appended to the composite */ public void addComposited(final Collection<E> compositeCollection) { all.add(compositeCollection); } /** * Add these Collections to the list of collections in this composite * * @param compositeCollection1 the Collection to be appended to the composite * @param compositeCollection2 the Collection to be appended to the composite */ public void addComposited(final Collection<E> compositeCollection1, final Collection<E> compositeCollection2) { all.add(compositeCollection1); all.add(compositeCollection2); } /** * Add these Collections to the list of collections in this composite * * @param compositeCollections the Collections to be appended to the composite */ public void addComposited(final Collection<E>... compositeCollections) { all.addAll(Arrays.asList(compositeCollections)); } /** * Removes a collection from the those being decorated in this composite. * * @param coll collection to be removed */ public void removeComposited(final Collection<E> coll) { all.remove(coll); } //----------------------------------------------------------------------- /** * Returns a new collection containing all of the elements * * @return A new ArrayList containing all of the elements in this composite. * The new collection is <i>not</i> backed by this composite. */ public Collection<E> toCollection() { return new ArrayList<E>(this); } /** * Gets the collections being decorated. * * @return Unmodifiable list of all collections in this composite. */ public List<Collection<E>> getCollections() { return UnmodifiableList.unmodifiableList(all); } /** * Get the collection mutator to be used for this CompositeCollection. * @return CollectionMutator<E> */ protected CollectionMutator<E> getMutator() { return mutator; } //----------------------------------------------------------------------- /** * Pluggable strategy to handle changes to the composite. * * @param <E> the element being held in the collection */ public interface CollectionMutator<E> extends Serializable { /** * Called when an object is to be added to the composite. * * @param composite the CompositeCollection being changed * @param collections all of the Collection instances in this CompositeCollection * @param obj the object being added * @return true if the collection is changed * @throws UnsupportedOperationException if add is unsupported * @throws ClassCastException if the object cannot be added due to its type * @throws NullPointerException if the object cannot be added because its null * @throws IllegalArgumentException if the object cannot be added */ boolean add(CompositeCollection<E> composite, List<Collection<E>> collections, E obj); /** * Called when a collection is to be added to the composite. * * @param composite the CompositeCollection being changed * @param collections all of the Collection instances in this CompositeCollection * @param coll the collection being added * @return true if the collection is changed * @throws UnsupportedOperationException if add is unsupported * @throws ClassCastException if the object cannot be added due to its type * @throws NullPointerException if the object cannot be added because its null * @throws IllegalArgumentException if the object cannot be added */ boolean addAll(CompositeCollection<E> composite, List<Collection<E>> collections, Collection<? extends E> coll); /** * Called when an object is to be removed to the composite. * * @param composite the CompositeCollection being changed * @param collections all of the Collection instances in this CompositeCollection * @param obj the object being removed * @return true if the collection is changed * @throws UnsupportedOperationException if removed is unsupported * @throws ClassCastException if the object cannot be removed due to its type * @throws NullPointerException if the object cannot be removed because its null * @throws IllegalArgumentException if the object cannot be removed */ boolean remove(CompositeCollection<E> composite, List<Collection<E>> collections, Object obj); } }