    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}