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 }