    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}