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