net.yetamine.lang.functional.Predicates Maven / Gradle / Ivy
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/*
* Copyright 2016 Yetamine
*
* Licensed 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 net.yetamine.lang.functional;
import java.util.Objects;
import java.util.function.Predicate;
/**
* A utility class providing several {@link Predicate} implementations.
*/
public final class Predicates {
/**
* Prevents creating instances of this class.
*/
private Predicates() {
throw new AssertionError();
}
/**
* Makes an instance from the given predicate.
*
*
* This method is a convenient factory method for fluent making a predicate:
*
*
* Predicates.from(MyUtilities::someTest).negate()
*
*
* @param
* the type of the parameter
* @param predicate
* the predicate to return. It must not be {@code null}.
*
* @return the predicate
*/
@SuppressWarnings("unchecked")
public static Predicate from(Predicate predicate) {
return (Predicate) predicate;
}
/**
* Returns a predicate that yields always {@code false}.
*
* @param
* the type of the parameter
*
* @return the predicate
*/
public static Predicate alwaysFalse() {
return t -> false;
}
/**
* Returns a predicate that yields always {@code true}.
*
* @param
* the type of the parameter
*
* @return the predicate
*/
public static Predicate alwaysTrue() {
return t -> true;
}
/**
* Returns a predicate that computes a conjunction of all given predicates;
* the computation uses short-circuit evaluation.
*
*
* This method does not make any copy of the input, therefore the caller may
* provide a dynamic underlying sequence, but on the other hand, the caller
* is responsible for thread safety of the sequence, so that another thread
* may iterate through the sequence, having a consistent snapshot.
*
*
* This method may be useful in the cases of a dynamic chain or when simply
* the sequence is long and chaining the predicates causes too deep call
* nesting.
*
* @param
* the type of the parameter
* @param sequence
* the sequence of the predicates to apply. It must not be
* {@code null} and it must not provide {@code null} elements.
*
* @return a predicate that computes a conjunction of all given predicates
*/
public static Predicate allOf(Iterable> sequence) {
Objects.requireNonNull(sequence);
return t -> {
for (Predicate predicate : sequence) {
if (!predicate.test(t)) {
return false;
}
}
return true;
};
}
/**
* Returns a predicate that computes a dijunction of all given predicates;
* the computation uses short-circuit evaluation.
*
*
* This method does not make any copy of the input, therefore the caller may
* provide a dynamic underlying sequence, but on the other hand, the caller
* is responsible for thread safety of the sequence, so that another thread
* may iterate through the sequence, having a consistent snapshot.
*
*
* This method may be useful in the cases of a dynamic chain or when simply
* the sequence is long and chaining the predicates causes too deep call
* nesting.
*
* @param
* the type of the parameter
* @param sequence
* the sequence of the predicates to apply. It must not be
* {@code null} and it must not provide {@code null} elements.
*
* @return a predicate that computes a disjunction of all given predicates
*/
public static Predicate noneOf(Iterable> sequence) {
Objects.requireNonNull(sequence);
return t -> {
for (Predicate predicate : sequence) {
if (predicate.test(t)) {
return false;
}
}
return true;
};
}
/**
* Returns a predicate that computes a dijunction of all given predicates;
* the computation uses short-circuit evaluation.
*
*
* This method does not make any copy of the input, therefore the caller may
* provide a dynamic underlying sequence, but on the other hand, the caller
* is responsible for thread safety of the sequence, so that another thread
* may iterate through the sequence, having a consistent snapshot.
*
*
* This method may be useful in the cases of a dynamic chain or when simply
* the sequence is long and chaining the predicates causes too deep call
* nesting.
*
* @param
* the type of the parameter
* @param sequence
* the sequence of the predicates to apply. It must not be
* {@code null} and it must not provide {@code null} elements.
*
* @return a predicate that computes a disjunction of all given predicates
*/
public static Predicate anyOf(Iterable> sequence) {
Objects.requireNonNull(sequence);
return t -> {
for (Predicate predicate : sequence) {
if (predicate.test(t)) {
return true;
}
}
return false;
};
}
}