    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.collections4.collection;
    018
    019import java.io.Serializable;
    020import java.lang.reflect.Array;
    021import java.util.ArrayList;
    022import java.util.Collection;
    023import java.util.Iterator;
    024import java.util.List;
    025import java.util.Objects;
    026import java.util.function.Predicate;
    027
    028import org.apache.commons.collections4.CollectionUtils;
    029import org.apache.commons.collections4.iterators.EmptyIterator;
    030import org.apache.commons.collections4.iterators.IteratorChain;
    031import org.apache.commons.collections4.list.UnmodifiableList;
    032
    033/**
    034 * Decorates a collection of other collections to provide a single unified view.
    035 * <p>
    036 * Changes made to this collection will actually be made on the decorated collection.
    037 * Add and remove operations require the use of a pluggable strategy. If no
    038 * strategy is provided then add and remove are unsupported.
    039 * </p>
    040 * @param <E> the type of the elements in the collection
    041 * @since 3.0
    042 */
    043public class CompositeCollection<E> implements Collection<E>, Serializable {
    044
    045    /**
    046     * Pluggable strategy to handle changes to the composite.
    047     *
    048     * @param <E> the element being held in the collection
    049     */
    050    public interface CollectionMutator<E> extends Serializable {
    051
    052        /**
    053         * Called when an object is to be added to the composite.
    054         *
    055         * @param composite  the CompositeCollection being changed
    056         * @param collections  all of the Collection instances in this CompositeCollection
    057         * @param obj  the object being added
    058         * @return true if the collection is changed
    059         * @throws UnsupportedOperationException if add is unsupported
    060         * @throws ClassCastException if the object cannot be added due to its type
    061         * @throws NullPointerException if the object cannot be added because its null
    062         * @throws IllegalArgumentException if the object cannot be added
    063         */
    064        boolean add(CompositeCollection<E> composite, List<Collection<E>> collections, E obj);
    065
    066        /**
    067         * Called when a collection is to be added to the composite.
    068         *
    069         * @param composite  the CompositeCollection being changed
    070         * @param collections  all of the Collection instances in this CompositeCollection
    071         * @param coll  the collection being added
    072         * @return true if the collection is changed
    073         * @throws UnsupportedOperationException if add is unsupported
    074         * @throws ClassCastException if the object cannot be added due to its type
    075         * @throws NullPointerException if the object cannot be added because its null
    076         * @throws IllegalArgumentException if the object cannot be added
    077         */
    078        boolean addAll(CompositeCollection<E> composite,
    079                              List<Collection<E>> collections,
    080                              Collection<? extends E> coll);
    081
    082        /**
    083         * Called when an object is to be removed to the composite.
    084         *
    085         * @param composite  the CompositeCollection being changed
    086         * @param collections  all of the Collection instances in this CompositeCollection
    087         * @param obj  the object being removed
    088         * @return true if the collection is changed
    089         * @throws UnsupportedOperationException if removed is unsupported
    090         * @throws ClassCastException if the object cannot be removed due to its type
    091         * @throws NullPointerException if the object cannot be removed because its null
    092         * @throws IllegalArgumentException if the object cannot be removed
    093         */
    094        boolean remove(CompositeCollection<E> composite,
    095                              List<Collection<E>> collections,
    096                              Object obj);
    097
    098    }
    099
    100    /** Serialization version */
    101    private static final long serialVersionUID = 8417515734108306801L;
    102
    103    /** CollectionMutator to handle changes to the collection */
    104    private CollectionMutator<E> mutator;
    105
    106    /** Collections in the composite */
    107    private final List<Collection<E>> all = new ArrayList<>();
    108
    109    /**
    110     * Create an empty CompositeCollection.
    111     */
    112    public CompositeCollection() {
    113    }
    114
    115    /**
    116     * Create a Composite Collection with one collection.
    117     *
    118     * @param compositeCollection  the Collection to be appended to the composite
    119     */
    120    public CompositeCollection(final Collection<E> compositeCollection) {
    121        addComposited(compositeCollection);
    122    }
    123
    124    /**
    125     * Create a Composite Collection with an array of collections.
    126     *
    127     * @param compositeCollections  the collections to composite
    128     */
    129    public CompositeCollection(final Collection<E>... compositeCollections) {
    130        addComposited(compositeCollections);
    131    }
    132
    133    /**
    134     * Create a Composite Collection with two collections.
    135     *
    136     * @param compositeCollection1  the Collection to be appended to the composite
    137     * @param compositeCollection2  the Collection to be appended to the composite
    138     */
    139    public CompositeCollection(final Collection<E> compositeCollection1,
    140                               final Collection<E> compositeCollection2) {
    141        addComposited(compositeCollection1, compositeCollection2);
    142    }
    143
    144    /**
    145     * Adds an object to the collection, throwing UnsupportedOperationException
    146     * unless a CollectionMutator strategy is specified.
    147     *
    148     * @param obj  the object to add
    149     * @return {@code true} if the collection was modified
    150     * @throws UnsupportedOperationException if CollectionMutator hasn't been set
    151     * @throws UnsupportedOperationException if add is unsupported
    152     * @throws ClassCastException if the object cannot be added due to its type
    153     * @throws NullPointerException if the object cannot be added because its null
    154     * @throws IllegalArgumentException if the object cannot be added
    155     */
    156    @Override
    157    public boolean add(final E obj) {
    158        if (mutator == null) {
    159            throw new UnsupportedOperationException(
    160                "add() is not supported on CompositeCollection without a CollectionMutator strategy");
    161        }
    162        return mutator.add(this, all, obj);
    163    }
    164
    165    /**
    166     * Adds a collection of elements to this collection, throwing
    167     * UnsupportedOperationException unless a CollectionMutator strategy is specified.
    168     *
    169     * @param coll  the collection to add
    170     * @return true if the collection was modified
    171     * @throws UnsupportedOperationException if CollectionMutator hasn't been set
    172     * @throws UnsupportedOperationException if add is unsupported
    173     * @throws ClassCastException if the object cannot be added due to its type
    174     * @throws NullPointerException if the object cannot be added because its null
    175     * @throws IllegalArgumentException if the object cannot be added
    176     */
    177    @Override
    178    public boolean addAll(final Collection<? extends E> coll) {
    179        if (mutator == null) {
    180            throw new UnsupportedOperationException(
    181                "addAll() is not supported on CompositeCollection without a CollectionMutator strategy");
    182        }
    183        return mutator.addAll(this, all, coll);
    184    }
    185
    186    /**
    187     * Add these Collections to the list of collections in this composite
    188     *
    189     * @param compositeCollection  the Collection to be appended to the composite
    190     */
    191    public void addComposited(final Collection<E> compositeCollection) {
    192        if (compositeCollection != null) {
    193            all.add(compositeCollection);
    194        }
    195    }
    196
    197    /**
    198     * Add these Collections to the list of collections in this composite
    199     *
    200     * @param compositeCollections  the Collections to be appended to the composite
    201     */
    202    public void addComposited(final Collection<E>... compositeCollections) {
    203        for (final Collection<E> compositeCollection : compositeCollections) {
    204            if (compositeCollection != null) {
    205                all.add(compositeCollection);
    206            }
    207        }
    208    }
    209
    210    /**
    211     * Add these Collections to the list of collections in this composite
    212     *
    213     * @param compositeCollection1  the Collection to be appended to the composite
    214     * @param compositeCollection2  the Collection to be appended to the composite
    215     */
    216    public void addComposited(final Collection<E> compositeCollection1,
    217                              final Collection<E> compositeCollection2) {
    218        if (compositeCollection1 != null) {
    219            all.add(compositeCollection1);
    220        }
    221        if (compositeCollection2 != null) {
    222            all.add(compositeCollection2);
    223        }
    224    }
    225
    226    /**
    227     * Removes all of the elements from this collection.
    228     * <p>
    229     * This implementation calls {@code clear()} on each collection.
    230     * </p>
    231     * @throws UnsupportedOperationException if clear is unsupported
    232     */
    233    @Override
    234    public void clear() {
    235        for (final Collection<E> coll : all) {
    236            coll.clear();
    237        }
    238    }
    239
    240    /**
    241     * Checks whether this composite collection contains the object.
    242     * <p>
    243     * This implementation calls {@code contains()} on each collection.
    244     * </p>
    245     * @param obj  the object to search for
    246     * @return true if obj is contained in any of the contained collections
    247     */
    248    @Override
    249    public boolean contains(final Object obj) {
    250        for (final Collection<E> item : all) {
    251            if (item.contains(obj)) {
    252                return true;
    253            }
    254        }
    255        return false;
    256    }
    257
    258    /**
    259     * Checks whether this composite contains all the elements in the specified collection.
    260     * <p>
    261     * This implementation calls {@code contains()} for each element in the
    262     * specified collection.
    263     * </p>
    264     * @param coll  the collection to check for
    265     * @return true if all elements contained
    266     */
    267    @Override
    268    public boolean containsAll(final Collection<?> coll) {
    269        if (coll == null) {
    270            return false;
    271        }
    272        for (final Object item : coll) {
    273            if (!contains(item)) {
    274                return false;
    275            }
    276        }
    277        return true;
    278    }
    279
    280    /**
    281     * Gets the collections being decorated.
    282     *
    283     * @return Unmodifiable list of all collections in this composite.
    284     */
    285    public List<Collection<E>> getCollections() {
    286        return UnmodifiableList.unmodifiableList(all);
    287    }
    288
    289    /**
    290     * Gets the collection mutator to be used for this CompositeCollection.
    291     * @return CollectionMutator&lt;E&gt;
    292     */
    293    protected CollectionMutator<E> getMutator() {
    294        return mutator;
    295    }
    296
    297    /**
    298     * Checks whether this composite collection is empty.
    299     * <p>
    300     * This implementation calls {@code isEmpty()} on each collection.
    301     * </p>
    302     * @return true if all of the contained collections are empty
    303     */
    304    @Override
    305    public boolean isEmpty() {
    306        for (final Collection<E> item : all) {
    307            if (!item.isEmpty()) {
    308                return false;
    309            }
    310        }
    311        return true;
    312    }
    313
    314    /**
    315     * Gets an iterator over all the collections in this composite.
    316     * <p>
    317     * This implementation uses an {@code IteratorChain}.
    318     * </p>
    319     * @return an {@code IteratorChain} instance which supports
    320     *  {@code remove()}. Iteration occurs over contained collections in
    321     *  the order they were added, but this behavior should not be relied upon.
    322     * @see IteratorChain
    323     */
    324    @Override
    325    public Iterator<E> iterator() {
    326        if (all.isEmpty()) {
    327            return EmptyIterator.<E>emptyIterator();
    328        }
    329        final IteratorChain<E> chain = new IteratorChain<>();
    330        all.forEach(item -> chain.addIterator(item.iterator()));
    331        return chain;
    332    }
    333
    334    /**
    335     * Removes an object from the collection, throwing UnsupportedOperationException
    336     * unless a CollectionMutator strategy is specified.
    337     *
    338     * @param obj  the object being removed
    339     * @return true if the collection is changed
    340     * @throws UnsupportedOperationException if removed is unsupported
    341     * @throws ClassCastException if the object cannot be removed due to its type
    342     * @throws NullPointerException if the object cannot be removed because its null
    343     * @throws IllegalArgumentException if the object cannot be removed
    344     */
    345    @Override
    346    public boolean remove(final Object obj) {
    347        if (mutator == null) {
    348            throw new UnsupportedOperationException(
    349                "remove() is not supported on CompositeCollection without a CollectionMutator strategy");
    350        }
    351        return mutator.remove(this, all, obj);
    352    }
    353
    354    /**
    355     * Removes the elements in the specified collection from this composite collection.
    356     * <p>
    357     * This implementation calls {@code removeAll} on each collection.
    358     * </p>
    359     * @param coll  the collection to remove
    360     * @return true if the collection was modified
    361     * @throws UnsupportedOperationException if removeAll is unsupported
    362     */
    363    @Override
    364    public boolean removeAll(final Collection<?> coll) {
    365        if (CollectionUtils.isEmpty(coll)) {
    366            return false;
    367        }
    368        boolean changed = false;
    369        for (final Collection<E> item : all) {
    370            changed |= item.removeAll(coll);
    371        }
    372        return changed;
    373    }
    374
    375    /**
    376     * Removes a collection from the those being decorated in this composite.
    377     *
    378     * @param coll  collection to be removed
    379     */
    380    public void removeComposited(final Collection<E> coll) {
    381        all.remove(coll);
    382    }
    383
    384    /**
    385     * Removes all of the elements of this collection that satisfy the given predicate from this composite collection.
    386     * <p>
    387     * This implementation calls {@code removeIf} on each collection.
    388     * </p>
    389     * @param filter  a predicate which returns true for elements to be removed
    390     * @return true if the collection was modified
    391     * @throws UnsupportedOperationException if removeIf is unsupported
    392     * @since 4.4
    393     */
    394    @Override
    395    public boolean removeIf(final Predicate<? super E> filter) {
    396        if (Objects.isNull(filter)) {
    397            return false;
    398        }
    399        boolean changed = false;
    400        for (final Collection<E> item : all) {
    401            changed |= item.removeIf(filter);
    402        }
    403        return changed;
    404    }
    405
    406    /**
    407     * Retains all the elements in the specified collection in this composite collection,
    408     * removing all others.
    409     * <p>
    410     * This implementation calls {@code retainAll()} on each collection.
    411     * </p>
    412     * @param coll  the collection to remove
    413     * @return true if the collection was modified
    414     * @throws UnsupportedOperationException if retainAll is unsupported
    415     */
    416    @Override
    417    public boolean retainAll(final Collection<?> coll) {
    418        boolean changed = false;
    419        if (coll != null) {
    420            for (final Collection<E> item : all) {
    421                changed |= item.retainAll(coll);
    422            }
    423        }
    424        return changed;
    425    }
    426
    427    /**
    428     * Specify a CollectionMutator strategy instance to handle changes.
    429     *
    430     * @param mutator  the mutator to use
    431     */
    432    public void setMutator(final CollectionMutator<E> mutator) {
    433        this.mutator = mutator;
    434    }
    435
    436    /**
    437     * Gets the size of this composite collection.
    438     * <p>
    439     * This implementation calls {@code size()} on each collection.
    440     * </p>
    441     * @return total number of elements in all contained containers
    442     */
    443    @Override
    444    public int size() {
    445        int size = 0;
    446        for (final Collection<E> item : all) {
    447            size += item.size();
    448        }
    449        return size;
    450    }
    451
    452    /**
    453     * Returns an array containing all of the elements in this composite.
    454     *
    455     * @return an object array of all the elements in the collection
    456     */
    457    @Override
    458    public Object[] toArray() {
    459        final Object[] result = new Object[size()];
    460        int i = 0;
    461        for (final Iterator<E> it = iterator(); it.hasNext(); i++) {
    462            result[i] = it.next();
    463        }
    464        return result;
    465    }
    466
    467    /**
    468     * Returns an object array, populating the supplied array if possible.
    469     * See {@code Collection} interface for full details.
    470     *
    471     * @param <T>  the type of the elements in the collection
    472     * @param array  the array to use, populating if possible
    473     * @return an array of all the elements in the collection
    474     */
    475    @Override
    476    @SuppressWarnings("unchecked")
    477    public <T> T[] toArray(final T[] array) {
    478        final int size = size();
    479        Object[] result = null;
    480        if (array.length >= size) {
    481            result = array;
    482        } else {
    483            result = (Object[]) Array.newInstance(array.getClass().getComponentType(), size);
    484        }
    485
    486        int offset = 0;
    487        for (final Collection<E> item : all) {
    488            for (final E e : item) {
    489                result[offset++] = e;
    490            }
    491        }
    492        if (result.length > size) {
    493            result[size] = null;
    494        }
    495        return (T[]) result;
    496    }
    497
    498    /**
    499     * Returns a new collection containing all of the elements
    500     *
    501     * @return A new ArrayList containing all of the elements in this composite.
    502     *         The new collection is <em>not</em> backed by this composite.
    503     */
    504    public Collection<E> toCollection() {
    505        return new ArrayList<>(this);
    506    }
    507
    508}
    509