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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.util.Comparator;
20  
21  import org.apache.commons.collections4.Bag;
22  import org.apache.commons.collections4.SortedBag;
23  
24  /**
25   * Decorates another {@link SortedBag} to synchronize its behaviour
26   * for a multi-threaded environment.
27   * <p>
28   * Methods are synchronized, then forwarded to the decorated bag.
29   * Iterators must be separately synchronized around the loop.
30   * </p>
31   * <p>
32   * This class is Serializable from Commons Collections 3.1.
33   * </p>
34   *
35   * @param <E> the type of elements in this bag
36   * @since 3.0
37   */
38  public class SynchronizedSortedBag<E> extends SynchronizedBag<E> implements SortedBag<E> {
39  
40      /** Serialization version */
41      private static final long serialVersionUID = 722374056718497858L;
42  
43      /**
44       * Factory method to create a synchronized sorted bag.
45       *
46       * @param <E> the type of the elements in the bag
47       * @param bag  the bag to decorate, must not be null
48       * @return a new synchronized SortedBag
49       * @throws NullPointerException if bag is null
50       * @since 4.0
51       */
52      public static <E> SynchronizedSortedBag<E> synchronizedSortedBag(final SortedBag<E> bag) {
53          return new SynchronizedSortedBag<>(bag);
54      }
55  
56      //-----------------------------------------------------------------------
57      /**
58       * Constructor that wraps (not copies).
59       *
60       * @param bag  the bag to decorate, must not be null
61       * @throws NullPointerException if bag is null
62       */
63      protected SynchronizedSortedBag(final SortedBag<E> bag) {
64          super(bag);
65      }
66  
67      /**
68       * Constructor that wraps (not copies).
69       *
70       * @param bag  the bag to decorate, must not be null
71       * @param lock  the lock to use, must not be null
72       * @throws NullPointerException if bag or lock is null
73       */
74      protected SynchronizedSortedBag(final Bag<E> bag, final Object lock) {
75          super(bag, lock);
76      }
77  
78      /**
79       * Gets the bag being decorated.
80       *
81       * @return the decorated bag
82       */
83      protected SortedBag<E> getSortedBag() {
84          return (SortedBag<E>) decorated();
85      }
86  
87      //-----------------------------------------------------------------------
88  
89      @Override
90      public synchronized E first() {
91          synchronized (lock) {
92              return getSortedBag().first();
93          }
94      }
95  
96      @Override
97      public synchronized E last() {
98          synchronized (lock) {
99              return getSortedBag().last();
100         }
101     }
102 
103     @Override
104     public synchronized Comparator<? super E> comparator() {
105         synchronized (lock) {
106             return getSortedBag().comparator();
107         }
108     }
109 
110 }