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}