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 * </p>
031 *
032 * @param <T> the type of the input to the predicate.
033 * @since 3.0
034 */
035public final class OnePredicate<T> extends AbstractQuantifierPredicate<T> {
036
037    /** Serial version UID */
038    private static final long serialVersionUID = -8125389089924745785L;
039
040    /**
041     * Creates the predicate.
042     *
043     * @param <T> the type that the predicate queries
044     * @param predicates  the predicates to check, cloned, not null
045     * @return the {@code one} predicate
046     * @throws NullPointerException if the predicates array is null
047     * @throws NullPointerException if any predicate in the array is null
048     */
049    public static <T> Predicate<T> onePredicate(final Collection<? extends Predicate<? super T>> predicates) {
050        final Predicate<? super T>[] preds = FunctorUtils.validate(predicates);
051        return new OnePredicate<>(preds);
052    }
053
054    /**
055     * Creates the predicate.
056     * <p>
057     * If the array is size zero, the predicate always returns false.
058     * If the array is size one, then that predicate is returned.
059     * </p>
060     *
061     * @param <T> the type that the predicate queries
062     * @param predicates  the predicates to check, cloned, not null
063     * @return the {@code any} predicate
064     * @throws NullPointerException if the predicates array is null
065     * @throws NullPointerException if any predicate in the array is null
066     */
067    @SuppressWarnings("unchecked")
068    public static <T> Predicate<T> onePredicate(final Predicate<? super T>... predicates) {
069        FunctorUtils.validate(predicates);
070        if (predicates.length == 0) {
071            return FalsePredicate.<T>falsePredicate();
072        }
073        if (predicates.length == 1) {
074            return (Predicate<T>) predicates[0];
075        }
076        // <T> not needed in Eclipse but needed by the command line compiler
077        return new OnePredicate<T>(FunctorUtils.copy(predicates));
078    }
079
080    /**
081     * Constructor that performs no validation.
082     * Use {@code onePredicate} if you want that.
083     *
084     * @param predicates  the predicates to check, not cloned, not null
085     */
086    public OnePredicate(final Predicate<? super T>... predicates) {
087        super(predicates);
088    }
089
090    /**
091     * Evaluates the predicate returning true if only one decorated predicate
092     * returns true.
093     *
094     * @param object  the input object
095     * @return true if only one decorated predicate returns true
096     */
097    @Override
098    public boolean test(final T object) {
099        boolean match = false;
100        for (final Predicate<? super T> iPredicate : iPredicates) {
101            if (iPredicate.test(object)) {
102                if (match) {
103                    return false;
104                }
105                match = true;
106            }
107        }
108        return match;
109    }
110
111}