FunctorUtils.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections4.functors;
import java.util.Collection;
import java.util.Objects;
import org.apache.commons.collections4.Closure;
import org.apache.commons.collections4.Predicate;
import org.apache.commons.collections4.Transformer;
/**
* Internal utilities for functors.
*
* @since 3.0
*/
final class FunctorUtils {
/**
* A very simple method that coerces Closure<? super T> to Closure<T>.
* <p>This method exists
* simply as centralized documentation and atomic unchecked warning
* suppression.
*
* @param <T> the type of object the returned closure should "accept"
* @param closure the closure to coerce.
* @return the coerced closure.
*/
@SuppressWarnings("unchecked")
static <T> Closure<T> coerce(final Closure<? super T> closure) {
return (Closure<T>) closure;
}
/**
* A very simple method that coerces Predicate<? super T> to Predicate<T>.
* Due to the {@link Predicate#evaluate(T)} method, Predicate<? super T> is
* able to be coerced to Predicate<T> without casting issues.
* <p>This method exists
* simply as centralised documentation and atomic unchecked warning
* suppression.
*
* @param <T> the type of object the returned predicate should "accept"
* @param predicate the predicate to coerce.
* @return the coerced predicate.
*/
@SuppressWarnings("unchecked")
static <T> Predicate<T> coerce(final Predicate<? super T> predicate) {
return (Predicate<T>) predicate;
}
/**
* A very simple method that coerces Transformer<? super I, ? extends O> to Transformer<I, O>.
* <p>This method exists
* simply as centralised documentation and atomic unchecked warning
* suppression.
*
* @param <I> the type of object the returned transformer should "accept"
* @param <O> the type of object the returned transformer should "produce"
* @param transformer the transformer to coerce.
* @return the coerced transformer.
*/
@SuppressWarnings("unchecked")
static <I, O> Transformer<I, O> coerce(final Transformer<? super I, ? extends O> transformer) {
return (Transformer<I, O>) transformer;
}
/**
* Clone the closures to ensure that the internal reference can't be messed with.
*
* @param closures the closures to copy
* @return the cloned closures
*/
@SuppressWarnings("unchecked")
static <E> Closure<E>[] copy(final Closure<? super E>... closures) {
if (closures == null) {
return null;
}
return (Closure<E>[]) closures.clone();
}
/**
* Clone the predicates to ensure that the internal reference can't be messed with.
* Due to the {@link Predicate#evaluate(T)} method, Predicate<? super T> is
* able to be coerced to Predicate<T> without casting issues.
*
* @param predicates the predicates to copy
* @return the cloned predicates
*/
@SuppressWarnings("unchecked")
static <T> Predicate<T>[] copy(final Predicate<? super T>... predicates) {
if (predicates == null) {
return null;
}
return (Predicate<T>[]) predicates.clone();
}
/**
* Copy method
*
* @param transformers the transformers to copy
* @return a clone of the transformers
*/
@SuppressWarnings("unchecked")
static <I, O> Transformer<I, O>[] copy(final Transformer<? super I, ? extends O>... transformers) {
if (transformers == null) {
return null;
}
return (Transformer<I, O>[]) transformers.clone();
}
/**
* Validate the closures to ensure that all is well.
*
* @param closures the closures to validate
*/
static void validate(final Closure<?>... closures) {
Objects.requireNonNull(closures, "closures");
for (int i = 0; i < closures.length; i++) {
if (closures[i] == null) {
throw new NullPointerException("closures[" + i + "]");
}
}
}
/**
* Validate the predicates to ensure that all is well.
*
* @param predicates the predicates to validate
* @return predicate array
*/
static <T> Predicate<? super T>[] validate(final Collection<? extends Predicate<? super T>> predicates) {
Objects.requireNonNull(predicates, "predicates");
// convert to array like this to guarantee iterator() ordering
@SuppressWarnings("unchecked") // OK
final Predicate<? super T>[] preds = new Predicate[predicates.size()];
int i = 0;
for (final Predicate<? super T> predicate : predicates) {
preds[i] = predicate;
if (preds[i] == null) {
throw new NullPointerException("predicates[" + i + "]");
}
i++;
}
return preds;
}
/**
* Validate the predicates to ensure that all is well.
*
* @param predicates the predicates to validate
*/
static void validate(final Predicate<?>... predicates) {
Objects.requireNonNull(predicates, "predicates");
for (int i = 0; i < predicates.length; i++) {
if (predicates[i] == null) {
throw new NullPointerException("predicates[" + i + "]");
}
}
}
/**
* Validate method
*
* @param transformers the transformers to validate
*/
static void validate(final Transformer<?, ?>... transformers) {
Objects.requireNonNull(transformers, "transformers");
for (int i = 0; i < transformers.length; i++) {
if (transformers[i] == null) {
throw new NullPointerException("transformers[" + i + "]");
}
}
}
/**
* Restricted constructor.
*/
private FunctorUtils() {
}
}