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 import java.util.Objects;
21
22 import org.apache.commons.collections4.Closure;
23 import org.apache.commons.collections4.Predicate;
24 import org.apache.commons.collections4.Transformer;
25
26 /**
27 * Internal utilities for functors.
28 *
29 * @since 3.0
30 */
31 final class FunctorUtils {
32
33 /**
34 * A very simple method that coerces Closure<? super T> to Closure<T>.
35 * <p>This method exists
36 * simply as centralized documentation and atomic unchecked warning
37 * suppression.
38 *
39 * @param <T> the type of object the returned closure should "accept"
40 * @param closure the closure to coerce.
41 * @return the coerced closure.
42 */
43 @SuppressWarnings("unchecked")
44 static <T> Closure<T> coerce(final Closure<? super T> closure) {
45 return (Closure<T>) closure;
46 }
47
48 /**
49 * A very simple method that coerces Predicate<? super T> to Predicate<T>.
50 * Due to the {@link Predicate#evaluate(T)} method, Predicate<? super T> is
51 * able to be coerced to Predicate<T> without casting issues.
52 * <p>This method exists
53 * simply as centralised documentation and atomic unchecked warning
54 * suppression.
55 *
56 * @param <T> the type of object the returned predicate should "accept"
57 * @param predicate the predicate to coerce.
58 * @return the coerced predicate.
59 */
60 @SuppressWarnings("unchecked")
61 static <T> Predicate<T> coerce(final Predicate<? super T> predicate) {
62 return (Predicate<T>) predicate;
63 }
64
65 /**
66 * A very simple method that coerces Transformer<? super I, ? extends O> to Transformer<I, O>.
67 * <p>This method exists
68 * simply as centralised documentation and atomic unchecked warning
69 * suppression.
70 *
71 * @param <I> the type of object the returned transformer should "accept"
72 * @param <O> the type of object the returned transformer should "produce"
73 * @param transformer the transformer to coerce.
74 * @return the coerced transformer.
75 */
76 @SuppressWarnings("unchecked")
77 static <I, O> Transformer<I, O> coerce(final Transformer<? super I, ? extends O> transformer) {
78 return (Transformer<I, O>) transformer;
79 }
80
81 /**
82 * Clone the closures to ensure that the internal reference can't be messed with.
83 *
84 * @param closures the closures to copy
85 * @return the cloned closures
86 */
87 @SuppressWarnings("unchecked")
88 static <E> Closure<E>[] copy(final Closure<? super E>... closures) {
89 if (closures == null) {
90 return null;
91 }
92 return (Closure<E>[]) closures.clone();
93 }
94
95 /**
96 * Clone the predicates to ensure that the internal reference can't be messed with.
97 * Due to the {@link Predicate#evaluate(T)} method, Predicate<? super T> is
98 * able to be coerced to Predicate<T> without casting issues.
99 *
100 * @param predicates the predicates to copy
101 * @return the cloned predicates
102 */
103 @SuppressWarnings("unchecked")
104 static <T> Predicate<T>[] copy(final Predicate<? super T>... predicates) {
105 if (predicates == null) {
106 return null;
107 }
108 return (Predicate<T>[]) predicates.clone();
109 }
110
111 /**
112 * Copy method
113 *
114 * @param transformers the transformers to copy
115 * @return a clone of the transformers
116 */
117 @SuppressWarnings("unchecked")
118 static <I, O> Transformer<I, O>[] copy(final Transformer<? super I, ? extends O>... transformers) {
119 if (transformers == null) {
120 return null;
121 }
122 return (Transformer<I, O>[]) transformers.clone();
123 }
124
125 /**
126 * Validate the closures to ensure that all is well.
127 *
128 * @param closures the closures to validate
129 */
130 static void validate(final Closure<?>... closures) {
131 Objects.requireNonNull(closures, "closures");
132 for (int i = 0; i < closures.length; i++) {
133 if (closures[i] == null) {
134 throw new NullPointerException("closures[" + i + "]");
135 }
136 }
137 }
138
139 /**
140 * Validate the predicates to ensure that all is well.
141 *
142 * @param predicates the predicates to validate
143 * @return predicate array
144 */
145 static <T> Predicate<? super T>[] validate(final Collection<? extends Predicate<? super T>> predicates) {
146 Objects.requireNonNull(predicates, "predicates");
147 // convert to array like this to guarantee iterator() ordering
148 @SuppressWarnings("unchecked") // OK
149 final Predicate<? super T>[] preds = new Predicate[predicates.size()];
150 int i = 0;
151 for (final Predicate<? super T> predicate : predicates) {
152 preds[i] = predicate;
153 if (preds[i] == null) {
154 throw new NullPointerException("predicates[" + i + "]");
155 }
156 i++;
157 }
158 return preds;
159 }
160
161 /**
162 * Validate the predicates to ensure that all is well.
163 *
164 * @param predicates the predicates to validate
165 */
166 static void validate(final Predicate<?>... predicates) {
167 Objects.requireNonNull(predicates, "predicates");
168 for (int i = 0; i < predicates.length; i++) {
169 if (predicates[i] == null) {
170 throw new NullPointerException("predicates[" + i + "]");
171 }
172 }
173 }
174
175 /**
176 * Validate method
177 *
178 * @param transformers the transformers to validate
179 */
180 static void validate(final Transformer<?, ?>... transformers) {
181 Objects.requireNonNull(transformers, "transformers");
182 for (int i = 0; i < transformers.length; i++) {
183 if (transformers[i] == null) {
184 throw new NullPointerException("transformers[" + i + "]");
185 }
186 }
187 }
188
189 /**
190 * Restricted constructor.
191 */
192 private FunctorUtils() {
193 }
194
195 }