    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    /**
    061     * Constructor that wraps (not copies).
    062     *
    063     * @param bag  the bag to decorate, must not be null
    064     * @throws NullPointerException if bag is null
    065     */
    066    public CollectionBag(final Bag<E> bag) {
    067        super(bag);
    068    }
    069
    070    //-----------------------------------------------------------------------
    071    /**
    072     * Write the collection out using a custom routine.
    073     *
    074     * @param out  the output stream
    075     * @throws IOException if an error occurs while writing to the stream
    076     */
    077    private void writeObject(final ObjectOutputStream out) throws IOException {
    078        out.defaultWriteObject();
    079        out.writeObject(decorated());
    080    }
    081
    082    /**
    083     * Read the collection in using a custom routine.
    084     *
    085     * @param in  the input stream
    086     * @throws IOException if an error occurs while reading from the stream
    087     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    088     * @throws ClassCastException if deserialised object has wrong type
    089     */
    090    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    091    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    092        in.defaultReadObject();
    093        setCollection((Collection<E>) in.readObject());
    094    }
    095
    096    //-----------------------------------------------------------------------
    097    // Collection interface
    098    //-----------------------------------------------------------------------
    099
    100    /**
    101     * <i>(Change)</i>
    102     * Returns <code>true</code> if the bag contains all elements in
    103     * the given collection, <b>not</b> respecting cardinality. That is,
    104     * if the given collection <code>coll</code> contains at least one of
    105     * every object contained in this object.
    106     *
    107     * @param coll  the collection to check against
    108     * @return <code>true</code> if the Bag contains at least one of every object in the collection
    109     */
    110    @Override
    111    public boolean containsAll(final Collection<?> coll) {
    112        final Iterator<?> e = coll.iterator();
    113        while (e.hasNext()) {
    114            if(!contains(e.next())) {
    115                return false;
    116            }
    117        }
    118        return true;
    119    }
    120
    121    /**
    122     * <i>(Change)</i>
    123     * Adds one copy of the specified object to the Bag.
    124     * <p>
    125     * Since this method always increases the size of the bag, it
    126     * will always return <code>true</code>.
    127     *
    128     * @param object  the object to add
    129     * @return <code>true</code>, always
    130     */
    131    @Override
    132    public boolean add(final E object) {
    133        return add(object, 1);
    134    }
    135
    136    @Override
    137    public boolean addAll(final Collection<? extends E> coll) {
    138        boolean changed = false;
    139        final Iterator<? extends E> i = coll.iterator();
    140        while (i.hasNext()) {
    141            final boolean added = add(i.next(), 1);
    142            changed = changed || added;
    143        }
    144        return changed;
    145    }
    146
    147    /**
    148     * <i>(Change)</i>
    149     * Removes the first occurrence of the given object from the bag.
    150     * <p>
    151     * This will also remove the object from the {@link #uniqueSet()} if the
    152     * bag contains no occurrence anymore of the object after this operation.
    153     *
    154     * @param object  the object to remove
    155     * @return <code>true</code> if this call changed the collection
    156     */
    157    @Override
    158    public boolean remove(final Object object) {
    159        return remove(object, 1);
    160    }
    161
    162    /**
    163     * <i>(Change)</i>
    164     * Remove all elements represented in the given collection,
    165     * <b>not</b> respecting cardinality. That is, remove <i>all</i>
    166     * occurrences of every object contained in the given collection.
    167     *
    168     * @param coll  the collection to remove
    169     * @return <code>true</code> if this call changed the collection
    170     */
    171    @Override
    172    public boolean removeAll(final Collection<?> coll) {
    173        if (coll != null) {
    174            boolean result = false;
    175            final Iterator<?> i = coll.iterator();
    176            while (i.hasNext()) {
    177                final Object obj = i.next();
    178                final boolean changed = remove(obj, getCount(obj));
    179                result = result || changed;
    180            }
    181            return result;
    182        }
    183        // let the decorated bag handle the case of null argument
    184        return decorated().removeAll(null);
    185    }
    186
    187    /**
    188     * <i>(Change)</i>
    189     * Remove any members of the bag that are not in the given collection,
    190     * <i>not</i> respecting cardinality. That is, any object in the given
    191     * collection <code>coll</code> will be retained in the bag with the same
    192     * number of copies prior to this operation. All other objects will be
    193     * completely removed from this bag.
    194     * <p>
    195     * This implementation iterates over the elements of this bag, checking
    196     * each element in turn to see if it's contained in <code>coll</code>.
    197     * If it's not contained, it's removed from this bag. As a consequence,
    198     * it is advised to use a collection type for <code>coll</code> that provides
    199     * a fast (e.g. O(1)) implementation of {@link Collection#contains(Object)}.
    200     *
    201     * @param coll  the collection to retain
    202     * @return <code>true</code> if this call changed the collection
    203     */
    204    @Override
    205    public boolean retainAll(final Collection<?> coll) {
    206        if (coll != null) {
    207            boolean modified = false;
    208            final Iterator<E> e = iterator();
    209            while (e.hasNext()) {
    210                if (!coll.contains(e.next())) {
    211                    e.remove();
    212                    modified = true;
    213                }
    214            }
    215            return modified;
    216        }
    217        // let the decorated bag handle the case of null argument
    218        return decorated().retainAll(null);
    219    }
    220
    221    //-----------------------------------------------------------------------
    222    // Bag interface
    223    //-----------------------------------------------------------------------
    224
    225    /**
    226     * <i>(Change)</i>
    227     * Adds <code>count</code> copies of the specified object to the Bag.
    228     * <p>
    229     * Since this method always increases the size of the bag, it
    230     * will always return <code>true</code>.
    231     *
    232     * @param object  the object to add
    233     * @param count  the number of copies to add
    234     * @return <code>true</code>, always
    235     */
    236    @Override
    237    public boolean add(final E object, final int count) {
    238        decorated().add(object, count);
    239        return true;
    240    }
    241
    242}