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 null.
025 *
026 * @since Commons Collections 3.0
027 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
028 *
029 * @author Stephen Colebourne
030 */
031 public final class NullIsTruePredicate implements Predicate, PredicateDecorator, Serializable {
032
033 /** Serial version UID */
034 private static final long serialVersionUID = -7625133768987126273L;
035
036 /** The predicate to decorate */
037 private final Predicate iPredicate;
038
039 /**
040 * Factory to create the null true predicate.
041 *
042 * @param predicate the predicate to decorate, not null
043 * @return the predicate
044 * @throws IllegalArgumentException if the predicate is null
045 */
046 public static Predicate getInstance(Predicate predicate) {
047 if (predicate == null) {
048 throw new IllegalArgumentException("Predicate must not be null");
049 }
050 return new NullIsTruePredicate(predicate);
051 }
052
053 /**
054 * Constructor that performs no validation.
055 * Use <code>getInstance</code> if you want that.
056 *
057 * @param predicate the predicate to call after the null check
058 */
059 public NullIsTruePredicate(Predicate predicate) {
060 super();
061 iPredicate = predicate;
062 }
063
064 /**
065 * Evaluates the predicate returning the result of the decorated predicate
066 * once a null check is performed.
067 *
068 * @param object the input object
069 * @return true if decorated predicate returns true or input is null
070 */
071 public boolean evaluate(Object object) {
072 if (object == null) {
073 return true;
074 }
075 return iPredicate.evaluate(object);
076 }
077
078 /**
079 * Gets the predicate being decorated.
080 *
081 * @return the predicate as the only element in an array
082 * @since Commons Collections 3.1
083 */
084 public Predicate[] getPredicates() {
085 return new Predicate[] {iPredicate};
086 }
087
088 }