    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 * The method javadoc highlights the differences compared to the original Bag interface.
    035 *
    036 * @see Bag
    037 * @param <E> the type of elements in this bag
    038 * @since 4.0
    039 */
    040public final class CollectionBag<E> extends AbstractBagDecorator<E> {
    041
    042    /** Serialization version */
    043    private static final long serialVersionUID = -2560033712679053143L;
    044
    045    /**
    046     * Factory method to create a bag that complies to the Collection contract.
    047     *
    048     * @param <E> the type of the elements in the bag
    049     * @param bag  the bag to decorate, must not be null
    050     * @return a Bag that complies to the Collection contract
    051     * @throws NullPointerException if bag is null
    052     */
    053    public static <E> Bag<E> collectionBag(final Bag<E> bag) {
    054        return new CollectionBag<>(bag);
    055    }
    056
    057    //-----------------------------------------------------------------------
    058    /**
    059     * Constructor that wraps (not copies).
    060     *
    061     * @param bag  the bag to decorate, must not be null
    062     * @throws NullPointerException if bag is null
    063     */
    064    public CollectionBag(final Bag<E> bag) {
    065        super(bag);
    066    }
    067
    068    //-----------------------------------------------------------------------
    069    /**
    070     * Write the collection out using a custom routine.
    071     *
    072     * @param out  the output stream
    073     * @throws IOException if an error occurs while writing to the stream
    074     */
    075    private void writeObject(final ObjectOutputStream out) throws IOException {
    076        out.defaultWriteObject();
    077        out.writeObject(decorated());
    078    }
    079
    080    /**
    081     * Read the collection in using a custom routine.
    082     *
    083     * @param in  the input stream
    084     * @throws IOException if an error occurs while reading from the stream
    085     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    086     * @throws ClassCastException if deserialised object has wrong type
    087     */
    088    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    089    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    090        in.defaultReadObject();
    091        setCollection((Collection<E>) in.readObject());
    092    }
    093
    094    //-----------------------------------------------------------------------
    095    // Collection interface
    096    //-----------------------------------------------------------------------
    097
    098    /**
    099     * <i>(Change)</i>
    100     * Returns <code>true</code> if the bag contains all elements in
    101     * the given collection, <b>not</b> respecting cardinality. That is,
    102     * if the given collection <code>coll</code> contains at least one of
    103     * every object contained in this object.
    104     *
    105     * @param coll  the collection to check against
    106     * @return <code>true</code> if the Bag contains at least one of every object in the collection
    107     */
    108    @Override
    109    public boolean containsAll(final Collection<?> coll) {
    110        final Iterator<?> e = coll.iterator();
    111        while (e.hasNext()) {
    112            if(!contains(e.next())) {
    113                return false;
    114            }
    115        }
    116        return true;
    117    }
    118
    119    /**
    120     * <i>(Change)</i>
    121     * Adds one copy of the specified object to the Bag.
    122     * <p>
    123     * Since this method always increases the size of the bag, it
    124     * will always return <code>true</code>.
    125     *
    126     * @param object  the object to add
    127     * @return <code>true</code>, always
    128     */
    129    @Override
    130    public boolean add(final E object) {
    131        return add(object, 1);
    132    }
    133
    134    @Override
    135    public boolean addAll(final Collection<? extends E> coll) {
    136        boolean changed = false;
    137        final Iterator<? extends E> i = coll.iterator();
    138        while (i.hasNext()) {
    139            final boolean added = add(i.next(), 1);
    140            changed = changed || added;
    141        }
    142        return changed;
    143    }
    144
    145    /**
    146     * <i>(Change)</i>
    147     * Removes the first occurrence of the given object from the bag.
    148     * <p>
    149     * This will also remove the object from the {@link #uniqueSet()} if the
    150     * bag contains no occurrence anymore of the object after this operation.
    151     *
    152     * @param object  the object to remove
    153     * @return <code>true</code> if this call changed the collection
    154     */
    155    @Override
    156    public boolean remove(final Object object) {
    157        return remove(object, 1);
    158    }
    159
    160    /**
    161     * <i>(Change)</i>
    162     * Remove all elements represented in the given collection,
    163     * <b>not</b> respecting cardinality. That is, remove <i>all</i>
    164     * occurrences of every object contained in the given collection.
    165     *
    166     * @param coll  the collection to remove
    167     * @return <code>true</code> if this call changed the collection
    168     */
    169    @Override
    170    public boolean removeAll(final Collection<?> coll) {
    171        if (coll != null) {
    172            boolean result = false;
    173            final Iterator<?> i = coll.iterator();
    174            while (i.hasNext()) {
    175                final Object obj = i.next();
    176                final boolean changed = remove(obj, getCount(obj));
    177                result = result || changed;
    178            }
    179            return result;
    180        }
    181        // let the decorated bag handle the case of null argument
    182        return decorated().removeAll(null);
    183    }
    184
    185    /**
    186     * <i>(Change)</i>
    187     * Remove any members of the bag that are not in the given collection,
    188     * <i>not</i> respecting cardinality. That is, any object in the given
    189     * collection <code>coll</code> will be retained in the bag with the same
    190     * number of copies prior to this operation. All other objects will be
    191     * completely removed from this bag.
    192     * <p>
    193     * This implementation iterates over the elements of this bag, checking
    194     * each element in turn to see if it's contained in <code>coll</code>.
    195     * If it's not contained, it's removed from this bag. As a consequence,
    196     * it is advised to use a collection type for <code>coll</code> that provides
    197     * a fast (e.g. O(1)) implementation of {@link Collection#contains(Object)}.
    198     *
    199     * @param coll  the collection to retain
    200     * @return <code>true</code> if this call changed the collection
    201     */
    202    @Override
    203    public boolean retainAll(final Collection<?> coll) {
    204        if (coll != null) {
    205            boolean modified = false;
    206            final Iterator<E> e = iterator();
    207            while (e.hasNext()) {
    208                if (!coll.contains(e.next())) {
    209                    e.remove();
    210                    modified = true;
    211                }
    212            }
    213            return modified;
    214        }
    215        // let the decorated bag handle the case of null argument
    216        return decorated().retainAll(null);
    217    }
    218
    219    //-----------------------------------------------------------------------
    220    // Bag interface
    221    //-----------------------------------------------------------------------
    222
    223    /**
    224     * <i>(Change)</i>
    225     * Adds <code>count</code> copies of the specified object to the Bag.
    226     * <p>
    227     * Since this method always increases the size of the bag, it
    228     * will always return <code>true</code>.
    229     *
    230     * @param object  the object to add
    231     * @param count  the number of copies to add
    232     * @return <code>true</code>, always
    233     */
    234    @Override
    235    public boolean add(final E object, final int count) {
    236        decorated().add(object, count);
    237        return true;
    238    }
    239
    240}