io.vavr.collection.Comparators Maven / Gradle / Ivy
/* __ __ __ __ __ ___
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*
* Copyright 2014-2020 Vavr, http://vavr.io
*
* 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 io.vavr.collection;
import java.io.Serializable;
import java.util.Comparator;
/**
* INTERNAL: Common {@code Comparator} related functions (not intended to be public).
*
* @author Daniel Dietrich
*/
final class Comparators {
private Comparators() {
}
/**
* Returns the natural comparator for type U, i.e. treating it as {@code Comparable}.
* The returned comparator is also {@code java.io.Serializable}.
*
* Please note that this will lead to runtime exceptions, if U is not Comparable.
*
* @param The type
* @return The natural Comparator of type U
*/
@SuppressWarnings("unchecked")
static Comparator naturalComparator() {
return NaturalComparator.instance();
}
}
final class NaturalComparator implements Comparator, Serializable {
private static final long serialVersionUID = 1L;
private static final NaturalComparator INSTANCE = new NaturalComparator<>();
private NaturalComparator() {
}
@SuppressWarnings("unchecked")
static NaturalComparator instance() {
return (NaturalComparator) INSTANCE;
}
@SuppressWarnings("unchecked")
@Override
public int compare(T o1, T o2) {
return ((Comparable) o1).compareTo(o2);
}
/** @see Comparator#equals(Object) */
@Override
public boolean equals(Object obj) {
return obj instanceof NaturalComparator;
}
@Override
public int hashCode() {
return 1;
}
/**
* Instance control for object serialization.
*
* @return The singleton instance of NaturalComparator.
* @see java.io.Serializable
*/
private Object readResolve() {
return INSTANCE;
}
}