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