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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.multiset;
18  
19  import java.io.IOException;
20  import java.io.ObjectInputStream;
21  import java.io.ObjectOutputStream;
22  import java.util.Collection;
23  import java.util.Iterator;
24  import java.util.Set;
25  import java.util.function.Predicate;
26  
27  import org.apache.commons.collections4.MultiSet;
28  import org.apache.commons.collections4.Unmodifiable;
29  import org.apache.commons.collections4.iterators.UnmodifiableIterator;
30  import org.apache.commons.collections4.set.UnmodifiableSet;
31  
32  /**
33   * Decorates another {@link MultiSet} to ensure it can't be altered.
34   * <p>
35   * Attempts to modify it will result in an UnsupportedOperationException.
36   * </p>
37   *
38   * @param <E> the type held in the multiset
39   * @since 4.1
40   */
41  public final class UnmodifiableMultiSet<E>
42          extends AbstractMultiSetDecorator<E> implements Unmodifiable {
43  
44      /** Serialization version */
45      private static final long serialVersionUID = 20150611L;
46  
47      /**
48       * Factory method to create an unmodifiable multiset.
49       * <p>
50       * If the multiset passed in is already unmodifiable, it is returned.
51       *
52       * @param <E>  the type of the elements in the multiset
53       * @param multiset  the multiset to decorate, may not be null
54       * @return an unmodifiable MultiSet
55       * @throws NullPointerException if multiset is null
56       */
57      public static <E> MultiSet<E> unmodifiableMultiSet(final MultiSet<? extends E> multiset) {
58          if (multiset instanceof Unmodifiable) {
59              @SuppressWarnings("unchecked") // safe to upcast
60              final MultiSet<E> tmpMultiSet = (MultiSet<E>) multiset;
61              return tmpMultiSet;
62          }
63          return new UnmodifiableMultiSet<>(multiset);
64      }
65  
66      //-----------------------------------------------------------------------
67      /**
68       * Constructor that wraps (not copies).
69       *
70       * @param multiset  the multiset to decorate, may not be null
71       * @throws NullPointerException if multiset is null
72       */
73      @SuppressWarnings("unchecked") // safe to upcast
74      private UnmodifiableMultiSet(final MultiSet<? extends E> multiset) {
75          super((MultiSet<E>) multiset);
76      }
77  
78      //-----------------------------------------------------------------------
79      /**
80       * Write the collection out using a custom routine.
81       *
82       * @param out  the output stream
83       * @throws IOException if an error occurs while writing to the stream
84       */
85      private void writeObject(final ObjectOutputStream out) throws IOException {
86          out.defaultWriteObject();
87          out.writeObject(decorated());
88      }
89  
90      /**
91       * Read the collection in using a custom routine.
92       *
93       * @param in  the input stream
94       * @throws IOException if an error occurs while reading from the stream
95       * @throws ClassNotFoundException if an object read from the stream can not be loaded
96       * @throws ClassCastException if deserialised object has wrong type
97       */
98      @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
99      private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
100         in.defaultReadObject();
101         setCollection((Collection<E>) in.readObject());
102     }
103 
104     //-----------------------------------------------------------------------
105     @Override
106     public Iterator<E> iterator() {
107         return UnmodifiableIterator.<E> unmodifiableIterator(decorated().iterator());
108     }
109 
110     @Override
111     public boolean add(final E object) {
112         throw new UnsupportedOperationException();
113     }
114 
115     @Override
116     public boolean addAll(final Collection<? extends E> coll) {
117         throw new UnsupportedOperationException();
118     }
119 
120     @Override
121     public void clear() {
122         throw new UnsupportedOperationException();
123     }
124 
125     @Override
126     public boolean remove(final Object object) {
127         throw new UnsupportedOperationException();
128     }
129 
130     /**
131      * @since 4.4
132      */
133     @Override
134     public boolean removeIf(Predicate<? super E> filter) {
135         throw new UnsupportedOperationException();
136     }
137 
138     @Override
139     public boolean removeAll(final Collection<?> coll) {
140         throw new UnsupportedOperationException();
141     }
142 
143     @Override
144     public boolean retainAll(final Collection<?> coll) {
145         throw new UnsupportedOperationException();
146     }
147 
148     //-----------------------------------------------------------------------
149     @Override
150     public int setCount(final E object, final int count) {
151         throw new UnsupportedOperationException();
152     }
153 
154     @Override
155     public int add(final E object, final int count) {
156         throw new UnsupportedOperationException();
157     }
158 
159     @Override
160     public int remove(final Object object, final int count) {
161         throw new UnsupportedOperationException();
162     }
163 
164     @Override
165     public Set<E> uniqueSet() {
166         final Set<E> set = decorated().uniqueSet();
167         return UnmodifiableSet.unmodifiableSet(set);
168     }
169 
170     @Override
171     public Set<MultiSet.Entry<E>> entrySet() {
172         final Set<MultiSet.Entry<E>> set = decorated().entrySet();
173         return UnmodifiableSet.unmodifiableSet(set);
174     }
175 
176 }