TreeBag


1   /*
2    *  Copyright 2002-2004 The Apache Software Foundation
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License");
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License.
15   */
16  package org.apache.commons.collections.bag;
17  
18  import java.io.IOException  ;
19  import java.io.ObjectInputStream  ;
20  import java.io.ObjectOutputStream  ;
21  import java.io.Serializable  ;
22  import java.util.Collection  ;
23  import java.util.Comparator  ;
24  import java.util.SortedMap  ;
25  import java.util.TreeMap  ;
26  
27  import org.apache.commons.collections.SortedBag;
28  
29  /**
30   * Implements <code>SortedBag</code>, using a <code>TreeMap</code> to provide
31   * the data storage. This is the standard implementation of a sorted bag.
32   * <p>
33   * Order will be maintained among the bag members and can be viewed through the
34   * iterator.
35   * <p>
36   * A <code>Bag</code> stores each object in the collection together with a
37   * count of occurrences. Extra methods on the interface allow multiple copies
38   * of an object to be added or removed at once. It is important to read the
39   * interface javadoc carefully as several methods violate the
40   * <code>Collection</code> interface specification.
41   *
42   * @since Commons Collections 3.0 (previously in main package v2.0)
43   * @version $Revision: 1.9 $ $Date: 2004/02/18 00:56:25 $
44   * 
45   * @author Chuck Burdick
46   * @author Stephen Colebourne
47   */
48  public class TreeBag
49          extends AbstractMapBag implements SortedBag, Serializable   {
50  
51      /** Serial version lock */
52      static final long serialVersionUID = -7740146511091606676L;
53      
54      /**
55       * Constructs an empty <code>TreeBag</code>.
56       */
57      public TreeBag() {
58          super(new TreeMap  ());
59      }
60  
61      /**
62       * Constructs an empty bag that maintains order on its unique
63       * representative members according to the given {@link Comparator}.
64       * 
65       * @param comparator  the comparator to use
66       */
67      public TreeBag(Comparator   comparator) {
68          super(new TreeMap  (comparator));
69      }
70  
71      /**
72       * Constructs a <code>TreeBag</code> containing all the members of the
73       * specified collection.
74       * 
75       * @param coll  the collection to copy into the bag
76       */
77      public TreeBag(Collection   coll) {
78          this();
79          addAll(coll);
80      }
81  
82      //-----------------------------------------------------------------------
83      public Object   first() {
84          return ((SortedMap  ) getMap()).firstKey();
85      }
86  
87      public Object   last() {
88          return ((SortedMap  ) getMap()).lastKey();
89      }
90  
91      public Comparator   comparator() {
92          return ((SortedMap  ) getMap()).comparator();
93      }
94  
95      //-----------------------------------------------------------------------
96      /**
97       * Write the bag out using a custom routine.
98       */
99      private void writeObject(ObjectOutputStream   out) throws IOException   {
100         out.defaultWriteObject();
101         out.writeObject(comparator());
102         super.doWriteObject(out);
103     }
104 
105     /**
106      * Read the bag in using a custom routine.
107      */
108     private void readObject(ObjectInputStream   in) throws IOException  , ClassNotFoundException   {
109         in.defaultReadObject();
110         Comparator   comp = (Comparator  ) in.readObject();
111         super.doReadObject(new TreeMap  (comp), in);
112     }
113     
114 }
115
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