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 exactly 1 value. This is done for efficiency of the in-memory representation, since
033     * many properties will have just a single value, while others will have multiple values.
034     * 
035     * @author Randall Hauch
036     */
037    @Immutable
038    public class BasicSingleValueProperty extends BasicProperty {
039    
040        protected final Object value;
041    
042        /**
043         * Create a property with a single value
044         * 
045         * @param name the property name
046         * @param value the property value (which may be null)
047         */
048        public BasicSingleValueProperty( Name name,
049                                         Object value ) {
050            super(name);
051            this.value = value;
052        }
053    
054        /**
055         * {@inheritDoc}
056         */
057        public boolean isEmpty() {
058            return false;
059        }
060    
061        /**
062         * {@inheritDoc}
063         */
064        public boolean isMultiple() {
065            return false;
066        }
067    
068        /**
069         * {@inheritDoc}
070         */
071        public boolean isSingle() {
072            return true;
073        }
074    
075        /**
076         * {@inheritDoc}
077         */
078        public int size() {
079            return 1;
080        }
081    
082        /**
083         * {@inheritDoc}
084         * 
085         * @see org.jboss.dna.graph.property.Property#getFirstValue()
086         */
087        public Object getFirstValue() {
088            return value;
089        }
090    
091        /**
092         * {@inheritDoc}
093         */
094        public Iterator<Object> iterator() {
095            return new ValueIterator();
096        }
097    
098        protected class ValueIterator implements Iterator<Object> {
099    
100            private boolean done = false;
101    
102            protected ValueIterator() {
103            }
104    
105            /**
106             * {@inheritDoc}
107             */
108            public boolean hasNext() {
109                return !done;
110            }
111    
112            /**
113             * {@inheritDoc}
114             */
115            public Object next() {
116                if (!done) {
117                    done = true;
118                    return BasicSingleValueProperty.this.value;
119                }
120                throw new NoSuchElementException();
121            }
122    
123            /**
124             * {@inheritDoc}
125             */
126            public void remove() {
127                throw new UnsupportedOperationException();
128            }
129    
130        }
131    
132    }