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Java > Open Source Codes > org > netbeans > modules > xml > catalog > lib > FilterIterator


1 /*
2  * The contents of this file are subject to the terms of the Common Development
3  * and Distribution License (the License). You may not use this file except in
4  * compliance with the License.
5  *
6  * You can obtain a copy of the License at http://www.netbeans.org/cddl.html
7  * or http://www.netbeans.org/cddl.txt.
8  *
9  * When distributing Covered Code, include this CDDL Header Notice in each file
10  * and include the License file at http://www.netbeans.org/cddl.txt.
11  * If applicable, add the following below the CDDL Header, with the fields
12  * enclosed by brackets [] replaced by your own identifying information:
13  * "Portions Copyrighted [year] [name of copyright owner]"
14  *
15  * The Original Software is NetBeans. The Initial Developer of the Original
16  * Software is Sun Microsystems, Inc. Portions Copyright 1997-2006 Sun
17  * Microsystems, Inc. All Rights Reserved.
18  */

19 package org.netbeans.modules.xml.catalog.lib;
20
21 import java.util.*;
22
23 /**
24  * Filter backend iterator by appling a filter rule.
25  *
26  * @author Petr Kuzel
27  * @version 1.0
28  */

29 public final class FilterIterator implements Iterator {
30
31     private final Iterator peer;
32     private final Filter filter;
33
34     /*
35      * Holds candidate for next() call. It is nulledt by the next() call.
36      */

37     private Object JavaDoc next;
38
39     public FilterIterator(Iterator it, Filter filter) {
40         if (it == null || filter == null)
41             throw new IllegalArgumentException JavaDoc("null not allowed"); // NOI18N
42
peer = it;
43         this.filter = filter;
44     }
45
46     public void remove() {
47         throw new UnsupportedOperationException JavaDoc();
48     }
49
50     /*
51      * Retunr <code>next</code> element if available and reset it.
52      */

53     public Object JavaDoc next() {
54         if (hasNext()) {
55            Object JavaDoc ret = next;
56            next = null;
57            return ret;
58         } else {
59            throw new NoSuchElementException();
60         }
61     }
62
63     /*
64      * Determine if there is a next element. Put it in <code>next</code> field.
65      */

66     public boolean hasNext() {
67         if (next != null) return true;
68
69         while (peer.hasNext()) {
70             next = peer.next();
71             if (filter.accept(next)) return true;
72         }
73         next = null;
74         return false;
75     }
76     
77     public static interface Filter {
78         public boolean accept(Object JavaDoc obj);
79     }
80 }
81
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