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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.collections.primitives.adapters.io;
18  
19  import java.io.IOException;
20  import java.io.Reader;
21  import java.util.NoSuchElementException;
22  
23  import org.apache.commons.collections.primitives.CharIterator;
24  
25  /**
26   * Adapts a {@link Reader} to the {@link CharIterator} interface.
27   * 
28   * @version $Revision: 480462 $ $Date: 2006-11-29 03:15:00 -0500 (Wed, 29 Nov 2006) $
29   * @author Rodney Waldhoff
30   */
31  public class ReaderCharIterator implements CharIterator {
32  
33      public ReaderCharIterator(Reader in) {
34          this.reader = in;
35      }
36  
37      public static CharIterator adapt(Reader in) {
38          return null == in ? null : new ReaderCharIterator(in);
39      }
40      
41      public boolean hasNext() {
42          ensureNextAvailable();
43          return (-1 != next);
44      }
45  
46      public char next() {
47          if(!hasNext()) {
48              throw new NoSuchElementException("No next element");
49          } else {
50              nextAvailable = false;
51              return (char)next;
52          }
53      }
54      
55      /**
56       * Not supported.
57       * @throws UnsupportedOperationException
58       */
59      public void remove() throws UnsupportedOperationException {
60          throw new UnsupportedOperationException("remove() is not supported here");
61      }
62  
63      private void ensureNextAvailable() {
64          if(!nextAvailable) {
65              readNext();
66          }
67      }
68  
69      private void readNext() {
70          try {
71              next = reader.read();
72              nextAvailable = true;
73          } catch(IOException e) {
74              // TODO: Use a tunnelled exception instead? 
75              // See http://radio.weblogs.com/0122027/2003/04/01.html#a7, for example            
76              throw new RuntimeException(e.toString());
77          }
78      }
79      
80      private Reader reader = null;
81      private boolean nextAvailable = false;
82      private int next;
83  
84  }