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1   /**
2    * This class is based on the Iterators.FilterIterator class from
3    * araSpect (araspect.sourceforge.net).  The original copyright follows ...
4    *
5    * =================================================================
6    * Copyright (c) 2001,2002 aragost ag, Z�rich, Switzerland.
7    * All rights reserved.
8    *
9    * This software is provided 'as-is', without any express or implied
10   * warranty. In no event will the authors be held liable for any
11   * damages arising from the use of this software.
12   *
13   * Permission is granted to anyone to use this software for any
14   * purpose, including commercial applications, and to alter it and
15   * redistribute it freely, subject to the following restrictions:
16   *
17   * 1. The origin of this software must not be misrepresented; you
18   *    must not claim that you wrote the original software. If you
19   *    use this software in a product, an acknowledgment in the
20   *    product documentation would be appreciated but is not required.
21   *
22   * 2. Altered source versions must be plainly marked as such, and
23   *    must not be misrepresented as being the original software.
24   *
25   * 3. This notice may not be removed or altered from any source
26   *    distribution.
27   *
28   * ==================================================================
29   *
30   * Changes (c) 2003 University Health Network include the following:
31   * - move to non-nested class
32   * - collapse inherited method remove()
33   * - accept iterator instead of object in constructor
34   * - moved to HAPI package
35   * - Predicate added as an inner class; also changed to an interface
36   *
37   * These changes are distributed under the same terms as the original (above). 
38   */
39  package ca.uhn.hl7v2.util;
40  
41  import java.util.*;
42  
43  public class FilterIterator<T> implements Iterator<T> {
44      
45      private Predicate<T> predicate;
46      private Iterator<T> iter;
47      private T nextObject;
48      private boolean nextObjectSet = false;
49      
50      public FilterIterator(Iterator<T> iter, Predicate<T> predicate) {
51          this.iter = iter;
52          this.predicate = predicate;
53      }
54      
55      public boolean hasNext() {
56          if (nextObjectSet) {
57              return true;
58          } else {
59              return setNextObject();
60          }
61      }
62      
63      public T next() {
64          if (!nextObjectSet) {
65              if (!setNextObject()) {
66                  throw new NoSuchElementException();
67              }
68          }
69          nextObjectSet = false;
70          return nextObject;
71      }
72      
73      /**
74       * Set nextObject to the next object. If there are no more
75       * objects then return false. Otherwise, return true.
76       */
77      private boolean setNextObject() {
78          while (iter.hasNext()) {
79              T object = iter.next();
80              if (predicate.evaluate(object)) {
81                  nextObject = object;
82                  nextObjectSet = true;
83                  return true;
84              }
85          }
86          return false;
87      }
88      
89      /** Throws UnsupportedOperationException */
90      public void remove() {
91          throw new UnsupportedOperationException();
92      }
93      
94      /**
95       * Interface for evaluating whether an object should be returned by the iterator
96       */
97      public interface Predicate<T> {
98          public boolean evaluate(T obj);
99      }
100     
101 }