001 /* 002 * JBoss DNA (http://www.jboss.org/dna) 003 * See the COPYRIGHT.txt file distributed with this work for information 004 * regarding copyright ownership. Some portions may be licensed 005 * to Red Hat, Inc. under one or more contributor license agreements. 006 * See the AUTHORS.txt file in the distribution for a full listing of 007 * individual contributors. 008 * 009 * JBoss DNA is free software. Unless otherwise indicated, all code in JBoss DNA 010 * is licensed to you under the terms of the GNU Lesser General Public License as 011 * published by the Free Software Foundation; either version 2.1 of 012 * the License, or (at your option) any later version. 013 * 014 * JBoss DNA is distributed in the hope that it will be useful, 015 * but WITHOUT ANY WARRANTY; without even the implied warranty of 016 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 017 * Lesser General Public License for more details. 018 * 019 * You should have received a copy of the GNU Lesser General Public 020 * License along with this software; if not, write to the Free 021 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 022 * 02110-1301 USA, or see the FSF site: http://www.fsf.org. 023 */ 024 package org.jboss.dna.graph.property.basic; 025 026 import java.util.Iterator; 027 import java.util.NoSuchElementException; 028 import net.jcip.annotations.Immutable; 029 import org.jboss.dna.graph.property.Name; 030 031 /** 032 * An immutable version of a property that has no values. This is done for efficiency of the in-memory representation, since many 033 * properties will have just a single value, while others will have multiple values. 034 * 035 * @author Randall Hauch 036 */ 037 @Immutable 038 public class BasicEmptyProperty extends BasicProperty { 039 040 private static final Iterator<Object> SHARED_ITERATOR = new EmptyIterator<Object>(); 041 042 /** 043 * Create a property with no values. 044 * 045 * @param name the property name 046 */ 047 public BasicEmptyProperty( Name name ) { 048 super(name); 049 } 050 051 /** 052 * {@inheritDoc} 053 */ 054 public boolean isEmpty() { 055 return true; 056 } 057 058 /** 059 * {@inheritDoc} 060 */ 061 public boolean isMultiple() { 062 return false; 063 } 064 065 /** 066 * {@inheritDoc} 067 */ 068 public boolean isSingle() { 069 return false; 070 } 071 072 /** 073 * {@inheritDoc} 074 */ 075 public int size() { 076 return 0; 077 } 078 079 /** 080 * {@inheritDoc} 081 * 082 * @see org.jboss.dna.graph.property.Property#getFirstValue() 083 */ 084 public Object getFirstValue() { 085 return null; 086 } 087 088 /** 089 * {@inheritDoc} 090 */ 091 public Iterator<Object> iterator() { 092 return SHARED_ITERATOR; 093 } 094 095 protected static class EmptyIterator<T> implements Iterator<T> { 096 097 protected EmptyIterator() { 098 } 099 100 /** 101 * {@inheritDoc} 102 */ 103 public boolean hasNext() { 104 return false; 105 } 106 107 /** 108 * {@inheritDoc} 109 */ 110 public T next() { 111 throw new NoSuchElementException(); 112 } 113 114 /** 115 * {@inheritDoc} 116 */ 117 public void remove() { 118 throw new UnsupportedOperationException(); 119 } 120 121 } 122 123 }