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.functors;
018    
019    import java.io.Serializable;
020    
021    import org.apache.commons.collections.Predicate;
022    
023    /**
024     * Predicate implementation that returns true if the input is the same object
025     * as the one stored in this predicate.
026     * 
027     * @since Commons Collections 3.0
028     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
029     *
030     * @author Stephen Colebourne
031     */
032    public final class IdentityPredicate implements Predicate, Serializable {
033    
034        /** Serial version UID */
035        private static final long serialVersionUID = -89901658494523293L;
036    
037        
038        /** The value to compare to */
039        private final Object iValue;
040        
041        /**
042         * Factory to create the identity predicate.
043         * 
044         * @param object  the object to compare to
045         * @return the predicate
046         * @throws IllegalArgumentException if the predicate is null
047         */
048        public static Predicate getInstance(Object object) {
049            if (object == null) {
050                return NullPredicate.INSTANCE;
051            }
052            return new IdentityPredicate(object);
053        }
054    
055        /**
056         * Constructor that performs no validation.
057         * Use <code>getInstance</code> if you want that.
058         * 
059         * @param object  the object to compare to
060         */
061        public IdentityPredicate(Object object) {
062            super();
063            iValue = object;
064        }
065    
066        /**
067         * Evaluates the predicate returning true if the input object is identical to
068         * the stored object.
069         * 
070         * @param object  the input object
071         * @return true if input is the same object as the stored value
072         */
073        public boolean evaluate(Object object) {
074            return (iValue == object);
075        }
076    
077        /**
078         * Gets the value.
079         * 
080         * @return the value
081         * @since Commons Collections 3.1
082         */
083        public Object getValue() {
084            return iValue;
085        }
086    
087    }