    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.bag;
    018
    019import java.io.IOException;
    020import java.io.ObjectInputStream;
    021import java.io.ObjectOutputStream;
    022import java.util.Collection;
    023import java.util.Iterator;
    024
    025import org.apache.commons.collections4.Bag;
    026
    027/**
    028 * Decorates another {@link Bag} to comply with the Collection contract.
    029 * <p>
    030 * By decorating an existing {@link Bag} instance with a {@link CollectionBag},
    031 * it can be safely passed on to methods that require Collection types that
    032 * are fully compliant with the Collection contract.
    033 * </p>
    034 * <p>
    035 * The method Javadoc highlights the differences compared to the original Bag interface.
    036 * </p>
    037 *
    038 * @see Bag
    039 * @param <E> the type of elements in this bag
    040 * @since 4.0
    041 */
    042public final class CollectionBag<E> extends AbstractBagDecorator<E> {
    043
    044    /** Serialization version */
    045    private static final long serialVersionUID = -2560033712679053143L;
    046
    047    /**
    048     * Factory method to create a bag that complies to the Collection contract.
    049     *
    050     * @param <E> the type of the elements in the bag
    051     * @param bag  the bag to decorate, must not be null
    052     * @return a Bag that complies to the Collection contract
    053     * @throws NullPointerException if bag is null
    054     */
    055    public static <E> Bag<E> collectionBag(final Bag<E> bag) {
    056        return new CollectionBag<>(bag);
    057    }
    058
    059    /**
    060     * Constructor that wraps (not copies).
    061     *
    062     * @param bag  the bag to decorate, must not be null
    063     * @throws NullPointerException if bag is null
    064     */
    065    public CollectionBag(final Bag<E> bag) {
    066        super(bag);
    067    }
    068
    069    /**
    070     * <em>(Change)</em> Adds one copy of the specified object to the Bag.
    071     * <p>
    072     * Since this method always increases the size of the bag, it will always return {@code true}.
    073     * </p>
    074     *
    075     * @param object the object to add
    076     * @return {@code true}, always
    077     * @throws ClassCastException if the class of the specified element prevents it from being added to this collection
    078     */
    079    @Override
    080    public boolean add(final E object) {
    081        return add(object, 1);
    082    }
    083
    084    /**
    085     * <em>(Change)</em>
    086     * Adds {@code count} copies of the specified object to the Bag.
    087     * <p>
    088     * Since this method always increases the size of the bag, it
    089     * will always return {@code true}.
    090     *
    091     * @param object  the object to add
    092     * @param count  the number of copies to add
    093     * @return {@code true}, always
    094     * @throws ClassCastException if the class of the specified element prevents it from being added to this collection
    095     */
    096    @Override
    097    public boolean add(final E object, final int count) {
    098        decorated().add(object, count);
    099        return true;
    100    }
    101
    102    @Override
    103    public boolean addAll(final Collection<? extends E> coll) {
    104        boolean changed = false;
    105        for (final E current : coll) {
    106            final boolean added = add(current, 1);
    107            changed = changed || added;
    108        }
    109        return changed;
    110    }
    111
    112    /**
    113     * <em>(Change)</em>
    114     * Returns {@code true} if the bag contains all elements in
    115     * the given collection, <strong>not</strong> respecting cardinality. That is,
    116     * if the given collection {@code coll} contains at least one of
    117     * every object contained in this object.
    118     *
    119     * @param coll  the collection to check against
    120     * @return {@code true} if the Bag contains at least one of every object in the collection
    121     */
    122    @Override
    123    public boolean containsAll(final Collection<?> coll) {
    124        return coll.stream().allMatch(this::contains);
    125    }
    126
    127    /**
    128     * Reads the collection in using a custom routine.
    129     *
    130     * @param in  the input stream
    131     * @throws IOException if an error occurs while reading from the stream
    132     * @throws ClassNotFoundException if an object read from the stream cannot be loaded
    133     * @throws ClassCastException if deserialized object has wrong type
    134     */
    135    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    136    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    137        in.defaultReadObject();
    138        setCollection((Collection<E>) in.readObject());
    139    }
    140
    141    /**
    142     * <em>(Change)</em>
    143     * Removes the first occurrence of the given object from the bag.
    144     * <p>
    145     * This will also remove the object from the {@link #uniqueSet()} if the
    146     * bag contains no occurrence anymore of the object after this operation.
    147     * </p>
    148     *
    149     * @param object  the object to remove
    150     * @return {@code true} if this call changed the collection
    151     */
    152    @Override
    153    public boolean remove(final Object object) {
    154        return remove(object, 1);
    155    }
    156
    157    /**
    158     * <em>(Change)</em>
    159     * Remove all elements represented in the given collection,
    160     * <strong>not</strong> respecting cardinality. That is, remove <em>all</em>
    161     * occurrences of every object contained in the given collection.
    162     *
    163     * @param coll  the collection to remove
    164     * @return {@code true} if this call changed the collection
    165     */
    166    @Override
    167    public boolean removeAll(final Collection<?> coll) {
    168        if (coll != null) {
    169            boolean result = false;
    170            for (final Object obj : coll) {
    171                final boolean changed = remove(obj, getCount(obj));
    172                result = result || changed;
    173            }
    174            return result;
    175        }
    176        // let the decorated bag handle the case of null argument
    177        return decorated().removeAll(null);
    178    }
    179
    180    /**
    181     * <em>(Change)</em>
    182     * Remove any members of the bag that are not in the given collection,
    183     * <em>not</em> respecting cardinality. That is, any object in the given
    184     * collection {@code coll} will be retained in the bag with the same
    185     * number of copies prior to this operation. All other objects will be
    186     * completely removed from this bag.
    187     * <p>
    188     * This implementation iterates over the elements of this bag, checking
    189     * each element in turn to see if it's contained in {@code coll}.
    190     * If it's not contained, it's removed from this bag. As a consequence,
    191     * it is advised to use a collection type for {@code coll} that provides
    192     * a fast (for example O(1)) implementation of {@link Collection#contains(Object)}.
    193     * </p>
    194     *
    195     * @param coll  the collection to retain
    196     * @return {@code true} if this call changed the collection
    197     */
    198    @Override
    199    public boolean retainAll(final Collection<?> coll) {
    200        if (coll != null) {
    201            boolean modified = false;
    202            final Iterator<E> e = iterator();
    203            while (e.hasNext()) {
    204                if (!coll.contains(e.next())) {
    205                    e.remove();
    206                    modified = true;
    207                }
    208            }
    209            return modified;
    210        }
    211        // let the decorated bag handle the case of null argument
    212        return decorated().retainAll(null);
    213    }
    214
    215    /**
    216     * Writes the collection out using a custom routine.
    217     *
    218     * @param out  the output stream
    219     * @throws IOException if an error occurs while writing to the stream
    220     */
    221    private void writeObject(final ObjectOutputStream out) throws IOException {
    222        out.defaultWriteObject();
    223        out.writeObject(decorated());
    224    }
    225
    226}