    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}