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Predicates.java
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Predicates.java
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/*
* 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.dubbo.common.function;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.function.Predicate;
import static java.lang.Boolean.TRUE;
import static java.util.stream.Stream.of;
/**
* The utilities class for Java {@link Predicate}
*
* @since 2.7.5
*/
public interface Predicates {
Predicate[] EMPTY_ARRAY = new Predicate[0];
/**
* {@link Predicate} always return <code>true</code>
*
* @param <T> the type to test
* @return <code>true</code>
*/
static <T> Predicate<T> alwaysTrue() {
return e -> true;
}
/**
* {@link Predicate} always return <code>false</code>
*
* @param <T> the type to test
* @return <code>false</code>
*/
static <T> Predicate<T> alwaysFalse() {
return e -> false;
}
static <E, T> Predicate<T> map(Function<E, Predicate<T>> function, E element) {
return function.apply(element);
}
//
// static <E, T> Predicate<T> map(Function<E, Predicate<T>> function, E... elements) {
// return and(predicates(function, elements));
// }
//
static <E, T> Predicate<T>[] predicates(Function<E, Predicate<T>> function, E... elements) {
return of(elements)
.map(e -> function.apply(e))
.toArray(Predicate[]::new);
}
static <E, T> Predicate<T>[] predicates(BiFunction<E, T, Predicate<T>> function, T value, E... elements) {
return of(elements)
.map(e -> function.apply(e, value))
.toArray(Predicate[]::new);
}
static <E, T> Predicate<T> predicate(BiFunction<E, T, Predicate<T>> function, T value, E... elements) {
return and(predicates(function, value, elements));
}
/**
* Convert a {@link Function} to {@link Predicate}
*
* @param function a {@link Function}
* @param <T> the type to test
* @return non-null
*/
static <T> Predicate<T> predicate(Function<T, Boolean> function) {
return t -> TRUE.equals(function.apply(t));
}
/**
* a composed predicate that represents a short-circuiting logical AND of {@link Predicate predicates}
*
* @param predicates {@link Predicate predicates}
* @param <T> the type to test
* @return non-null
*/
static <T> Predicate<T> and(Predicate<T>... predicates) {
return of(predicates).reduce((a, b) -> a.and(b)).orElseGet(Predicates::alwaysTrue);
}
/**
* a composed predicate that represents a short-circuiting logical OR of {@link Predicate predicates}
*
* @param predicates {@link Predicate predicates}
* @param <T> the detected type
* @return non-null
*/
static <T> Predicate<T> or(Predicate<T>... predicates) {
return of(predicates).reduce((a, b) -> a.or(b)).orElse(e -> true);
}
}