001/* 002 * Copyright 2001 (C) MetaStuff, Ltd. All Rights Reserved. 003 * 004 * This software is open source. 005 * See the bottom of this file for the licence. 006 * 007 * $Id: FilterIterator.java,v 1.3 2001/08/01 09:17:21 jstrachan Exp $ 008 */ 009 010package org.dom4j.tree; 011 012import java.util.Iterator; 013import java.util.NoSuchElementException; 014 015/** <p><code>FilterIterator</code> is an abstract base class which is useful 016 * for implementors of {@link Iterator} which filter an existing iterator. 017 * 018 * @author <a href="mailto:james.strachan@metastuff.com">James Strachan</a> 019 * @version $Revision: 1.3 $ 020 */ 021public abstract class FilterIterator implements Iterator { 022 023 protected Iterator proxy; 024 private Object next; 025 private boolean first = true; 026 027 public FilterIterator(Iterator proxy) { 028 this.proxy = proxy; 029 } 030 031 032 public boolean hasNext() { 033 if ( first ) { 034 next = findNext(); 035 first = false; 036 } 037 return next != null; 038 } 039 040 public Object next() throws NoSuchElementException { 041 if ( ! hasNext() ) { 042 throw new NoSuchElementException(); 043 } 044 Object answer = this.next; 045 this.next = findNext(); 046 return answer; 047 } 048 049 public void remove() { 050 if (proxy != null) { 051 proxy.remove(); 052 } 053 } 054 055 /** Filter method to perform some matching on the given element. 056 * 057 * @return true if the given element matches the filter 058 * and should be appear in the iteration 059 */ 060 protected abstract boolean matches(Object element); 061 062 063 protected Object findNext() { 064 if ( proxy != null ) { 065 while (proxy.hasNext()) { 066 Object next = proxy.next(); 067 if ( next != null && matches(next) ) { 068 return next; 069 } 070 } 071 proxy = null; 072 } 073 return null; 074 } 075} 076 077 078 079 080/* 081 * Redistribution and use of this software and associated documentation 082 * ("Software"), with or without modification, are permitted provided 083 * that the following conditions are met: 084 * 085 * 1. Redistributions of source code must retain copyright 086 * statements and notices. Redistributions must also contain a 087 * copy of this document. 088 * 089 * 2. Redistributions in binary form must reproduce the 090 * above copyright notice, this list of conditions and the 091 * following disclaimer in the documentation and/or other 092 * materials provided with the distribution. 093 * 094 * 3. The name "DOM4J" must not be used to endorse or promote 095 * products derived from this Software without prior written 096 * permission of MetaStuff, Ltd. For written permission, 097 * please contact dom4j-info@metastuff.com. 098 * 099 * 4. Products derived from this Software may not be called "DOM4J" 100 * nor may "DOM4J" appear in their names without prior written 101 * permission of MetaStuff, Ltd. DOM4J is a registered 102 * trademark of MetaStuff, Ltd. 103 * 104 * 5. Due credit should be given to the DOM4J Project 105 * (http://dom4j.org/). 106 * 107 * THIS SOFTWARE IS PROVIDED BY METASTUFF, LTD. AND CONTRIBUTORS 108 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT 109 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 110 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL 111 * METASTUFF, LTD. OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 112 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 113 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 114 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 115 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 116 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 117 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 118 * OF THE POSSIBILITY OF SUCH DAMAGE. 119 * 120 * Copyright 2001 (C) MetaStuff, Ltd. All Rights Reserved. 121 * 122 * $Id: FilterIterator.java,v 1.3 2001/08/01 09:17:21 jstrachan Exp $ 123 */