001    /*
002     *  Licensed to the Apache Software Foundation (ASF) under one or more
003     *  contributor license agreements.  See the NOTICE file distributed with
004     *  this work for additional information regarding copyright ownership.
005     *  The ASF licenses this file to You under the Apache License, Version 2.0
006     *  (the "License"); you may not use this file except in compliance with
007     *  the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     *  Unless required by applicable law or agreed to in writing, software
012     *  distributed under the License is distributed on an "AS IS" BASIS,
013     *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     *  See the License for the specific language governing permissions and
015     *  limitations under the License.
016     */
017    package org.apache.commons.collections.bag;
018    
019    import java.util.Comparator;
020    
021    import org.apache.commons.collections.Bag;
022    import org.apache.commons.collections.SortedBag;
023    
024    /**
025     * Decorates another <code>SortedBag</code> to synchronize its behaviour
026     * for a multi-threaded environment.
027     * <p>
028     * Methods are synchronized, then forwarded to the decorated bag.
029     * Iterators must be separately synchronized around the loop.
030     * <p>
031     * This class is Serializable from Commons Collections 3.1.
032     *
033     * @since Commons Collections 3.0
034     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
035     * 
036     * @author Stephen Colebourne
037     */
038    public class SynchronizedSortedBag
039            extends SynchronizedBag implements SortedBag {
040    
041        /** Serialization version */
042        private static final long serialVersionUID = 722374056718497858L;
043    
044        /**
045         * Factory method to create a synchronized sorted bag.
046         * 
047         * @param bag  the bag to decorate, must not be null
048         * @return a new synchronized SortedBag
049         * @throws IllegalArgumentException if bag is null
050         */
051        public static SortedBag decorate(SortedBag bag) {
052            return new SynchronizedSortedBag(bag);
053        }
054        
055        //-----------------------------------------------------------------------
056        /**
057         * Constructor that wraps (not copies).
058         * 
059         * @param bag  the bag to decorate, must not be null
060         * @throws IllegalArgumentException if bag is null
061         */
062        protected SynchronizedSortedBag(SortedBag bag) {
063            super(bag);
064        }
065    
066        /**
067         * Constructor that wraps (not copies).
068         * 
069         * @param bag  the bag to decorate, must not be null
070         * @param lock  the lock to use, must not be null
071         * @throws IllegalArgumentException if bag is null
072         */
073        protected SynchronizedSortedBag(Bag bag, Object lock) {
074            super(bag, lock);
075        }
076    
077        /**
078         * Gets the bag being decorated.
079         * 
080         * @return the decorated bag
081         */
082        protected SortedBag getSortedBag() {
083            return (SortedBag) collection;
084        }
085        
086        //-----------------------------------------------------------------------
087        public synchronized Object first() {
088            synchronized (lock) {
089                return getSortedBag().first();
090            }
091        }
092    
093        public synchronized Object last() {
094            synchronized (lock) {
095                return getSortedBag().last();
096            }
097        }
098    
099        public synchronized Comparator comparator() {
100            synchronized (lock) {
101                return getSortedBag().comparator();
102            }
103        }
104    
105    }