1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections4.bag;
18
19 import java.io.IOException;
20 import java.io.ObjectInputStream;
21 import java.io.ObjectOutputStream;
22 import java.io.Serializable;
23 import java.util.Collection;
24 import java.util.Comparator;
25 import java.util.Objects;
26 import java.util.SortedMap;
27 import java.util.TreeMap;
28
29 import org.apache.commons.collections4.SortedBag;
30
31 /**
32 * Implements {@link SortedBag}, using a {@link TreeMap} to provide the data storage.
33 * This is the standard implementation of a sorted bag.
34 * <p>
35 * Order will be maintained among the bag members and can be viewed through the iterator.
36 * </p>
37 * <p>
38 * A {@link org.apache.commons.collections4.Bag Bag} stores each object in the collection
39 * together with a count of occurrences. Extra methods on the interface allow multiple
40 * copies of an object to be added or removed at once. It is important to read the interface
41 * Javadoc carefully as several methods violate the {@link Collection} interface specification.
42 * </p>
43 *
44 * @param <E> the type of elements in this bag
45 * @since 3.0 (previously in main package v2.0)
46 */
47 public class TreeBag<E> extends AbstractMapBag<E> implements SortedBag<E>, Serializable {
48
49 /** Serial version lock */
50 private static final long serialVersionUID = -7740146511091606676L;
51
52 /**
53 * Constructs an empty {@link TreeBag}.
54 */
55 public TreeBag() {
56 super(new TreeMap<>());
57 }
58
59 /**
60 * Constructs a {@link TreeBag} containing all the members of the
61 * specified collection.
62 *
63 * @param coll the collection to copy into the bag
64 */
65 public TreeBag(final Collection<? extends E> coll) {
66 this();
67 addAll(coll);
68 }
69
70 /**
71 * Constructs an empty bag that maintains order on its unique representative
72 * members according to the given {@link Comparator}.
73 *
74 * @param comparator the comparator to use
75 */
76 public TreeBag(final Comparator<? super E> comparator) {
77 super(new TreeMap<>(comparator));
78 }
79
80 /**
81 * Constructs a bag containing all the members of the given Iterable.
82 *
83 * @param iterable an iterable to copy into this bag.
84 * @since 4.5.0-M3
85 */
86 public TreeBag(final Iterable<? extends E> iterable) {
87 super(new TreeMap<>(), iterable);
88 }
89
90 /**
91 * {@inheritDoc}
92 *
93 * @throws IllegalArgumentException if the object to be added does not implement
94 * {@link Comparable} and the {@link TreeBag} is using natural ordering
95 * @throws NullPointerException if the specified key is null and this bag uses
96 * natural ordering, or its comparator does not permit null keys
97 */
98 @Override
99 public boolean add(final E object) {
100 if (comparator() == null && !(object instanceof Comparable)) {
101 Objects.requireNonNull(object, "object");
102 throw new IllegalArgumentException("Objects of type " + object.getClass() + " cannot be added to " +
103 "a naturally ordered TreeBag as it does not implement Comparable");
104 }
105 return super.add(object);
106 }
107
108 @Override
109 public Comparator<? super E> comparator() {
110 return getMap().comparator();
111 }
112
113 @Override
114 public E first() {
115 return getMap().firstKey();
116 }
117
118 @Override
119 protected SortedMap<E, AbstractMapBag.MutableInteger> getMap() {
120 return (SortedMap<E, AbstractMapBag.MutableInteger>) super.getMap();
121 }
122
123 @Override
124 public E last() {
125 return getMap().lastKey();
126 }
127
128 /**
129 * Deserializes the bag in using a custom routine.
130 *
131 * @param in the input stream
132 * @throws IOException if an error occurs while reading from the stream
133 * @throws ClassNotFoundException if an object read from the stream cannot be loaded
134 */
135 private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
136 in.defaultReadObject();
137 @SuppressWarnings("unchecked") // This will fail at runtime if the stream is incorrect
138 final Comparator<? super E> comp = (Comparator<? super E>) in.readObject();
139 super.doReadObject(new TreeMap<>(comp), in);
140 }
141
142 /**
143 * Serializes this object to an ObjectOutputStream.
144 *
145 * @param out the target ObjectOutputStream.
146 * @throws IOException thrown when an I/O errors occur writing to the target stream.
147 */
148 private void writeObject(final ObjectOutputStream out) throws IOException {
149 out.defaultWriteObject();
150 out.writeObject(comparator());
151 super.doWriteObject(out);
152 }
153
154 }