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.util.Collection;
020
021import org.apache.commons.collections4.Predicate;
022
023/**
024 * Predicate implementation that returns true if only one of the
025 * predicates return true.
026 * If the array of predicates is empty, then this predicate returns false.
027 * <p>
028 * NOTE: In versions prior to 3.2 an array size of zero or one
029 * threw an exception.
030 *
031 * @since 3.0
032 */
033public final class OnePredicate<T> extends AbstractQuantifierPredicate<T> {
034
035    /** Serial version UID */
036    private static final long serialVersionUID = -8125389089924745785L;
037
038    /**
039     * Factory to create the predicate.
040     * <p>
041     * If the array is size zero, the predicate always returns false.
042     * If the array is size one, then that predicate is returned.
043     *
044     * @param <T> the type that the predicate queries
045     * @param predicates  the predicates to check, cloned, not null
046     * @return the <code>any</code> predicate
047     * @throws NullPointerException if the predicates array is null
048     * @throws NullPointerException if any predicate in the array is null
049     */
050    @SuppressWarnings("unchecked")
051    public static <T> Predicate<T> onePredicate(final Predicate<? super T>... predicates) {
052        FunctorUtils.validate(predicates);
053        if (predicates.length == 0) {
054            return FalsePredicate.<T>falsePredicate();
055        }
056        if (predicates.length == 1) {
057            return (Predicate<T>) predicates[0];
058        }
059        return new OnePredicate<>(FunctorUtils.copy(predicates));
060    }
061
062    /**
063     * Factory to create the predicate.
064     *
065     * @param <T> the type that the predicate queries
066     * @param predicates  the predicates to check, cloned, not null
067     * @return the <code>one</code> predicate
068     * @throws NullPointerException if the predicates array is null
069     * @throws NullPointerException if any predicate in the array is null
070     */
071    public static <T> Predicate<T> onePredicate(final Collection<? extends Predicate<? super T>> predicates) {
072        final Predicate<? super T>[] preds = FunctorUtils.validate(predicates);
073        return new OnePredicate<>(preds);
074    }
075
076    /**
077     * Constructor that performs no validation.
078     * Use <code>onePredicate</code> if you want that.
079     *
080     * @param predicates  the predicates to check, not cloned, not null
081     */
082    public OnePredicate(final Predicate<? super T>... predicates) {
083        super(predicates);
084    }
085
086    /**
087     * Evaluates the predicate returning true if only one decorated predicate
088     * returns true.
089     *
090     * @param object  the input object
091     * @return true if only one decorated predicate returns true
092     */
093    @Override
094    public boolean evaluate(final T object) {
095        boolean match = false;
096        for (final Predicate<? super T> iPredicate : iPredicates) {
097            if (iPredicate.evaluate(object)) {
098                if (match) {
099                    return false;
100                }
101                match = true;
102            }
103        }
104        return match;
105    }
106
107}