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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.bag;
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.Bag;
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 Bag} to ensure it can't be altered.
34   * <p>
35   * This class is Serializable from Commons Collections 3.1.
36   * </p>
37   * <p>
38   * Attempts to modify it will result in an UnsupportedOperationException.
39   * </p>
40   *
41   * @param <E> the type of elements in this bag
42   * @since 3.0
43   */
44  public final class UnmodifiableBag<E>
45          extends AbstractBagDecorator<E> implements Unmodifiable {
46  
47      /** Serialization version */
48      private static final long serialVersionUID = -1873799975157099624L;
49  
50      /**
51       * Factory method to create an unmodifiable bag.
52       * <p>
53       * If the bag passed in is already unmodifiable, it is returned.
54       *
55       * @param <E> the type of the elements in the bag
56       * @param bag  the bag to decorate, must not be null
57       * @return an unmodifiable Bag
58       * @throws NullPointerException if bag is null
59       * @since 4.0
60       */
61      public static <E> Bag<E> unmodifiableBag(final Bag<? extends E> bag) {
62          if (bag instanceof Unmodifiable) {
63              @SuppressWarnings("unchecked") // safe to upcast
64              final Bag<E> tmpBag = (Bag<E>) bag;
65              return tmpBag;
66          }
67          return new UnmodifiableBag<>(bag);
68      }
69  
70      //-----------------------------------------------------------------------
71      /**
72       * Constructor that wraps (not copies).
73       *
74       * @param bag  the bag to decorate, must not be null
75       * @throws NullPointerException if bag is null
76       */
77      @SuppressWarnings("unchecked") // safe to upcast
78      private UnmodifiableBag(final Bag<? extends E> bag) {
79          super((Bag<E>) bag);
80      }
81  
82      //-----------------------------------------------------------------------
83      /**
84       * Write the collection out using a custom routine.
85       *
86       * @param out  the output stream
87       * @throws IOException if an error occurs while writing to the stream
88       */
89      private void writeObject(final ObjectOutputStream out) throws IOException {
90          out.defaultWriteObject();
91          out.writeObject(decorated());
92      }
93  
94      /**
95       * Read the collection in using a custom routine.
96       *
97       * @param in  the input stream
98       * @throws IOException if an error occurs while reading from the stream
99       * @throws ClassNotFoundException if an object read from the stream can not be loaded
100      * @throws ClassCastException if deserialised object has wrong type
101      */
102     @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
103     private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
104         in.defaultReadObject();
105         setCollection((Collection<E>) in.readObject());
106     }
107 
108     //-----------------------------------------------------------------------
109     @Override
110     public Iterator<E> iterator() {
111         return UnmodifiableIterator.<E> unmodifiableIterator(decorated().iterator());
112     }
113 
114     @Override
115     public boolean add(final E object) {
116         throw new UnsupportedOperationException();
117     }
118 
119     @Override
120     public boolean addAll(final Collection<? extends E> coll) {
121         throw new UnsupportedOperationException();
122     }
123 
124     @Override
125     public void clear() {
126         throw new UnsupportedOperationException();
127     }
128 
129     @Override
130     public boolean remove(final Object object) {
131         throw new UnsupportedOperationException();
132     }
133 
134     /**
135      * @since 4.4
136      */
137     @Override
138     public boolean removeIf(Predicate<? super E> filter) {
139         throw new UnsupportedOperationException();
140     }
141 
142     @Override
143     public boolean removeAll(final Collection<?> coll) {
144         throw new UnsupportedOperationException();
145     }
146 
147     @Override
148     public boolean retainAll(final Collection<?> coll) {
149         throw new UnsupportedOperationException();
150     }
151 
152     //-----------------------------------------------------------------------
153     @Override
154     public boolean add(final E object, final int count) {
155         throw new UnsupportedOperationException();
156     }
157 
158     @Override
159     public boolean remove(final Object object, final int count) {
160         throw new UnsupportedOperationException();
161     }
162 
163     @Override
164     public Set<E> uniqueSet() {
165         final Set<E> set = decorated().uniqueSet();
166         return UnmodifiableSet.<E> unmodifiableSet(set);
167     }
168 
169 }