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.Predicate;
022    import org.apache.commons.collections.SortedBag;
023    
024    /**
025     * Decorates another <code>SortedBag</code> to validate that additions
026     * match a specified predicate.
027     * <p>
028     * This bag exists to provide validation for the decorated bag.
029     * It is normally created to decorate an empty bag.
030     * If an object cannot be added to the bag, an IllegalArgumentException is thrown.
031     * <p>
032     * One usage would be to ensure that no null entries are added to the bag.
033     * <pre>SortedBag bag = PredicatedSortedBag.decorate(new TreeBag(), NotNullPredicate.INSTANCE);</pre>
034     * <p>
035     * This class is Serializable from Commons Collections 3.1.
036     *
037     * @since Commons Collections 3.0
038     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
039     * 
040     * @author Stephen Colebourne
041     * @author Paul Jack
042     */
043    public class PredicatedSortedBag
044            extends PredicatedBag implements SortedBag {
045    
046        /** Serialization version */
047        private static final long serialVersionUID = 3448581314086406616L;
048    
049        /**
050         * Factory method to create a predicated (validating) bag.
051         * <p>
052         * If there are any elements already in the bag being decorated, they
053         * are validated.
054         * 
055         * @param bag  the bag to decorate, must not be null
056         * @param predicate  the predicate to use for validation, must not be null
057         * @return a new predicated SortedBag
058         * @throws IllegalArgumentException if bag or predicate is null
059         * @throws IllegalArgumentException if the bag contains invalid elements
060         */
061        public static SortedBag decorate(SortedBag bag, Predicate predicate) {
062            return new PredicatedSortedBag(bag, predicate);
063        }
064    
065        //-----------------------------------------------------------------------
066        /**
067         * Constructor that wraps (not copies).
068         * <p>
069         * If there are any elements already in the bag being decorated, they
070         * are validated.
071         * 
072         * @param bag  the bag to decorate, must not be null
073         * @param predicate  the predicate to use for validation, must not be null
074         * @throws IllegalArgumentException if bag or predicate is null
075         * @throws IllegalArgumentException if the bag contains invalid elements
076         */
077        protected PredicatedSortedBag(SortedBag bag, Predicate predicate) {
078            super(bag, predicate);
079        }
080    
081        /**
082         * Gets the decorated sorted bag.
083         * 
084         * @return the decorated bag
085         */
086        protected SortedBag getSortedBag() {
087            return (SortedBag) getCollection();
088        }
089        
090        //-----------------------------------------------------------------------
091        public Object first() {
092            return getSortedBag().first();
093        }
094    
095        public Object last() {
096            return getSortedBag().last();
097        }
098    
099        public Comparator comparator() {
100            return getSortedBag().comparator();
101        }
102    
103    }