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.io.Serializable;
023import java.util.Collection;
024import java.util.Comparator;
025import java.util.SortedMap;
026import java.util.TreeMap;
027
028import org.apache.commons.collections4.SortedBag;
029
030/**
031 * Implements {@link SortedBag}, using a {@link TreeMap} to provide the data storage.
032 * This is the standard implementation of a sorted bag.
033 * <p>
034 * Order will be maintained among the bag members and can be viewed through the iterator.
035 * </p>
036 * <p>
037 * A {@link org.apache.commons.collections4.Bag Bag} stores each object in the collection
038 * together with a count of occurrences. Extra methods on the interface allow multiple
039 * copies of an object to be added or removed at once. It is important to read the interface
040 * javadoc carefully as several methods violate the {@link Collection} interface specification.
041 * </p>
042 *
043 * @param <E> the type of elements in this bag
044 * @since 3.0 (previously in main package v2.0)
045 */
046public class TreeBag<E> extends AbstractMapBag<E> implements SortedBag<E>, Serializable {
047
048    /** Serial version lock */
049    private static final long serialVersionUID = -7740146511091606676L;
050
051    /**
052     * Constructs an empty {@link TreeBag}.
053     */
054    public TreeBag() {
055        super(new TreeMap<E, MutableInteger>());
056    }
057
058    /**
059     * Constructs an empty bag that maintains order on its unique representative
060     * members according to the given {@link Comparator}.
061     *
062     * @param comparator the comparator to use
063     */
064    public TreeBag(final Comparator<? super E> comparator) {
065        super(new TreeMap<E, MutableInteger>(comparator));
066    }
067
068    /**
069     * Constructs a {@link TreeBag} containing all the members of the
070     * specified collection.
071     *
072     * @param coll the collection to copy into the bag
073     */
074    public TreeBag(final Collection<? extends E> coll) {
075        this();
076        addAll(coll);
077    }
078
079    //-----------------------------------------------------------------------
080    /**
081     * {@inheritDoc}
082     *
083     * @throws IllegalArgumentException if the object to be added does not implement
084     * {@link Comparable} and the {@link TreeBag} is using natural ordering
085     * @throws NullPointerException if the specified key is null and this bag uses
086     * natural ordering, or its comparator does not permit null keys
087     */
088    @Override
089    public boolean add(final E object) {
090        if(comparator() == null && !(object instanceof Comparable)) {
091            if (object == null) {
092                throw new NullPointerException();
093            }
094            throw new IllegalArgumentException("Objects of type " + object.getClass() + " cannot be added to " +
095                                               "a naturally ordered TreeBag as it does not implement Comparable");
096        }
097        return super.add(object);
098    }
099
100    //-----------------------------------------------------------------------
101
102    @Override
103    public E first() {
104        return getMap().firstKey();
105    }
106
107    @Override
108    public E last() {
109        return getMap().lastKey();
110    }
111
112    @Override
113    public Comparator<? super E> comparator() {
114        return getMap().comparator();
115    }
116
117    @Override
118    protected SortedMap<E, AbstractMapBag.MutableInteger> getMap() {
119        return (SortedMap<E, AbstractMapBag.MutableInteger>) super.getMap();
120    }
121
122    //-----------------------------------------------------------------------
123    /**
124     * Write the bag out using a custom routine.
125     *
126     * @param out  the output stream
127     * @throws IOException if an error occurs while writing to the stream
128     */
129    private void writeObject(final ObjectOutputStream out) throws IOException {
130        out.defaultWriteObject();
131        out.writeObject(comparator());
132        super.doWriteObject(out);
133    }
134
135    /**
136     * Read the bag in using a custom routine.
137     *
138     * @param in  the input stream
139     * @throws IOException if an error occurs while reading from the stream
140     * @throws ClassNotFoundException if an object read from the stream can not be loaded
141     */
142    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
143        in.defaultReadObject();
144        @SuppressWarnings("unchecked")  // This will fail at runtime if the stream is incorrect
145        final Comparator<? super E> comp = (Comparator<? super E>) in.readObject();
146        super.doReadObject(new TreeMap<E, MutableInteger>(comp), in);
147    }
148
149}