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 */
017package org.apache.commons.collections4.functors;
018
019import java.io.Serializable;
020
021import org.apache.commons.collections4.Predicate;
022
023/**
024 * Predicate implementation that returns true if the input is null.
025 *
026 * @since 3.0
027 */
028public final class NullIsTruePredicate<T> implements PredicateDecorator<T>, Serializable {
029
030    /** Serial version UID */
031    private static final long serialVersionUID = -7625133768987126273L;
032
033    /** The predicate to decorate */
034    private final Predicate<? super T> iPredicate;
035
036    /**
037     * Factory to create the null true predicate.
038     *
039     * @param <T> the type that the predicate queries
040     * @param predicate  the predicate to decorate, not null
041     * @return the predicate
042     * @throws NullPointerException if the predicate is null
043     */
044    public static <T> Predicate<T> nullIsTruePredicate(final Predicate<? super T> predicate) {
045        if (predicate == null) {
046            throw new NullPointerException("Predicate must not be null");
047        }
048        return new NullIsTruePredicate<>(predicate);
049    }
050
051    /**
052     * Constructor that performs no validation.
053     * Use <code>nullIsTruePredicate</code> if you want that.
054     *
055     * @param predicate  the predicate to call after the null check
056     */
057    public NullIsTruePredicate(final Predicate<? super T> predicate) {
058        super();
059        iPredicate = predicate;
060    }
061
062    /**
063     * Evaluates the predicate returning the result of the decorated predicate
064     * once a null check is performed.
065     *
066     * @param object  the input object
067     * @return true if decorated predicate returns true or input is null
068     */
069    @Override
070    public boolean evaluate(final T object) {
071        if (object == null) {
072            return true;
073        }
074        return iPredicate.evaluate(object);
075    }
076
077    /**
078     * Gets the predicate being decorated.
079     *
080     * @return the predicate as the only element in an array
081     * @since 3.1
082     */
083    @Override
084    @SuppressWarnings("unchecked")
085    public Predicate<? super T>[] getPredicates() {
086        return new Predicate[] { iPredicate };
087    }
088
089}