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 * {@inheritDoc}
82 *
83 * @throws IllegalArgumentException if the object to be added does not implement
84 * {@link Comparable} and the {@link TreeBag} is using natural ordering
85 * @throws NullPointerException if the specified key is null and this bag uses
86 * natural ordering, or its comparator does not permit null keys
87 */
88 @Override
89 public boolean add(final E object) {
90 if (comparator() == null && !(object instanceof Comparable)) {
91 Objects.requireNonNull(object, "object");
92 throw new IllegalArgumentException("Objects of type " + object.getClass() + " cannot be added to " +
93 "a naturally ordered TreeBag as it does not implement Comparable");
94 }
95 return super.add(object);
96 }
97
98 @Override
99 public Comparator<? super E> comparator() {
100 return getMap().comparator();
101 }
102
103 @Override
104 public E first() {
105 return getMap().firstKey();
106 }
107
108 @Override
109 protected SortedMap<E, AbstractMapBag.MutableInteger> getMap() {
110 return (SortedMap<E, AbstractMapBag.MutableInteger>) super.getMap();
111 }
112
113 @Override
114 public E last() {
115 return getMap().lastKey();
116 }
117
118 /**
119 * Read the bag in using a custom routine.
120 *
121 * @param in the input stream
122 * @throws IOException if an error occurs while reading from the stream
123 * @throws ClassNotFoundException if an object read from the stream can not be loaded
124 */
125 private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
126 in.defaultReadObject();
127 @SuppressWarnings("unchecked") // This will fail at runtime if the stream is incorrect
128 final Comparator<? super E> comp = (Comparator<? super E>) in.readObject();
129 super.doReadObject(new TreeMap<>(comp), in);
130 }
131
132 /**
133 * Write the bag out using a custom routine.
134 *
135 * @param out the output stream
136 * @throws IOException if an error occurs while writing to the stream
137 */
138 private void writeObject(final ObjectOutputStream out) throws IOException {
139 out.defaultWriteObject();
140 out.writeObject(comparator());
141 super.doWriteObject(out);
142 }
143
144 }