1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections4.functors;
18
19 import java.util.Collection;
20
21 import org.apache.commons.collections4.Predicate;
22
23 /**
24 * Predicate implementation that returns true if only one of the
25 * predicates return true.
26 * If the array of predicates is empty, then this predicate returns false.
27 * <p>
28 * NOTE: In versions prior to 3.2 an array size of zero or one
29 * threw an exception.
30 * </p>
31 *
32 * @since 3.0
33 */
34 public final class OnePredicate<T> extends AbstractQuantifierPredicate<T> {
35
36 /** Serial version UID */
37 private static final long serialVersionUID = -8125389089924745785L;
38
39 /**
40 * Factory to create the predicate.
41 *
42 * @param <T> the type that the predicate queries
43 * @param predicates the predicates to check, cloned, not null
44 * @return the {@code one} predicate
45 * @throws NullPointerException if the predicates array is null
46 * @throws NullPointerException if any predicate in the array is null
47 */
48 public static <T> Predicate<T> onePredicate(final Collection<? extends Predicate<? super T>> predicates) {
49 final Predicate<? super T>[] preds = FunctorUtils.validate(predicates);
50 return new OnePredicate<>(preds);
51 }
52
53 /**
54 * Factory to create the predicate.
55 * <p>
56 * If the array is size zero, the predicate always returns false.
57 * If the array is size one, then that predicate is returned.
58 *
59 * @param <T> the type that the predicate queries
60 * @param predicates the predicates to check, cloned, not null
61 * @return the {@code any} predicate
62 * @throws NullPointerException if the predicates array is null
63 * @throws NullPointerException if any predicate in the array is null
64 */
65 @SuppressWarnings("unchecked")
66 public static <T> Predicate<T> onePredicate(final Predicate<? super T>... predicates) {
67 FunctorUtils.validate(predicates);
68 if (predicates.length == 0) {
69 return FalsePredicate.<T>falsePredicate();
70 }
71 if (predicates.length == 1) {
72 return (Predicate<T>) predicates[0];
73 }
74 return new OnePredicate<>(FunctorUtils.copy(predicates));
75 }
76
77 /**
78 * Constructor that performs no validation.
79 * Use {@code onePredicate} if you want that.
80 *
81 * @param predicates the predicates to check, not cloned, not null
82 */
83 public OnePredicate(final Predicate<? super T>... predicates) {
84 super(predicates);
85 }
86
87 /**
88 * Evaluates the predicate returning true if only one decorated predicate
89 * returns true.
90 *
91 * @param object the input object
92 * @return true if only one decorated predicate returns true
93 */
94 @Override
95 public boolean evaluate(final T object) {
96 boolean match = false;
97 for (final Predicate<? super T> iPredicate : iPredicates) {
98 if (iPredicate.evaluate(object)) {
99 if (match) {
100 return false;
101 }
102 match = true;
103 }
104 }
105 return match;
106 }
107
108 }