MultiMapNamesEnumeration


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  
18  package org.apache.tomcat.util.collections;
19  
20  import java.util.Enumeration  ;
21  
22  /** Enumerate the distinct header names.
23      Each nextElement() is O(n) ( a comparation is
24      done with all previous elements ).
25  
26      This is less frequesnt than add() -
27      we want to keep add O(1).
28  */
29  public final class MultiMapNamesEnumeration implements Enumeration   {
30      int pos;
31      int size;
32      String   next;
33      MultiMap headers;
34  
35      // toString and unique options are not implemented -
36      // we allways to toString and unique.
37      
38      /** Create a new multi-map enumeration.
39       * @param  headers the collection to enumerate 
40       * @param  toString convert each name to string 
41       * @param  unique return only unique names
42       */
43      MultiMapNamesEnumeration(MultiMap headers, boolean toString,
44                   boolean unique) {
45      this.headers=headers;
46      pos=0;
47      size = headers.size();
48      findNext();
49      }
50  
51      private void findNext() {
52      next=null;
53      for(  ; pos< size; pos++ ) {
54          next=headers.getName( pos ).toString();
55          for( int j=0; j<pos ; j++ ) {
56          if( headers.getName( j ).equalsIgnoreCase( next )) {
57              // duplicate.
58              next=null;
59              break;
60          }
61          }
62          if( next!=null ) {
63          // it's not a duplicate
64          break;
65          }
66      }
67      // next time findNext is called it will try the
68      // next element
69      pos++;
70      }
71      
72      public boolean hasMoreElements() {
73      return next!=null;
74      }
75  
76      public Object   nextElement() {
77      String   current=next;
78      findNext();
79      return current;
80      }
81  }
82
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