1 /** 2 * The utillib library. 3 * More information is available at http://www.jinchess.com/. 4 * Copyright (C) 2003 Alexander Maryanovsky. 5 * All rights reserved. 6 * 7 * The utillib library is free software; you can redistribute 8 * it and/or modify it under the terms of the GNU Lesser General Public License 9 * as published by the Free Software Foundation; either version 2 of the 10 * License, or (at your option) any later version. 11 * 12 * The utillib library is distributed in the hope that it will 13 * be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser 15 * General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public License 18 * along with utillib library; if not, write to the Free Software 19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 20 */ 21 22 package free.util; 23 24 import java.util.Enumeration; 25 import java.util.NoSuchElementException; 26 27 28 /** 29 * An implementation of the <code>Enumeration</code> interface which delegates 30 * to another <code>Enumeration</code>, but only returns elements which pass 31 * the {@link #accept(Object)} method. 32 */ 33 34 public abstract class FilteringEnumeration implements Enumeration{ 35 36 37 38 /** 39 * The delegate enumeration. 40 */ 41 42 private final Enumeration delegate; 43 44 45 46 /** 47 * The next element we'll return. This is set by the <code>findNext</code> 48 * method. 49 */ 50 51 private Object next = null; 52 53 54 55 /** 56 * Creates a new <code>FilteringEnumeration</code> object with the specified 57 * delegate. 58 */ 59 FilteringEnumeration(Enumeration delegate)60 public FilteringEnumeration(Enumeration delegate){ 61 this.delegate = delegate; 62 } 63 64 65 66 /** 67 * Finds the next element in the delegate enumeration which passes 68 * <code>accept</code> and puts it in <code>next</code>. 69 */ 70 findNext()71 private void findNext(){ 72 if (next != null) 73 return; 74 75 while (delegate.hasMoreElements()){ 76 Object element = delegate.nextElement(); 77 if (accept(element)){ 78 next = element; 79 break; 80 } 81 } 82 } 83 84 85 86 /** 87 * Returns whether there are more elements in this <code>Enumeration</code>. 88 */ 89 hasMoreElements()90 public boolean hasMoreElements(){ 91 findNext(); 92 93 return next != null; 94 } 95 96 97 98 /** 99 * Returns the next element in the delegate enumeration which passes the 100 * <code>accept</code> method. 101 */ 102 nextElement()103 public Object nextElement() throws NoSuchElementException{ 104 findNext(); 105 106 if (next == null) 107 throw new NoSuchElementException(); 108 109 Object result = next; 110 next = null; 111 return result; 112 } 113 114 115 116 /** 117 * Returns whether the specified object passes the filter. 118 */ 119 accept(Object element)120 public abstract boolean accept(Object element); 121 122 123 124 }