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/*     / \____  _    _  ____   ______  / \ ____  __    _______
 *    /  /    \/ \  / \/    \ /  /\__\/  //    \/  \  //  /\__\   JΛVΛSLΛNG
 *  _/  /  /\  \  \/  /  /\  \\__\\  \  //  /\  \ /\\/ \ /__\ \   Copyright 2014-2016 Javaslang, http://javaslang.io
 * /___/\_/  \_/\____/\_/  \_/\__\/__/\__\_/  \_//  \__/\_____/   Licensed under the Apache License, Version 2.0
 */
package javaslang.collection;

import java.io.Serializable;
import java.util.Comparator;

/**
 * INTERNAL API - This class is subject to change.
 */
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  SerializableComparator naturalComparator() {
        return (o1, o2) -> ((Comparable) o1).compareTo(o2);
    }

    /**
     * Needed for serialization of sortable collections which internally need a comparator.
     * 

     * In general the comparator may be
     * 

     * a concrete class
     * a lambda
     * a method reference
     * 

     *
     * @param  the type of objects that may be compared by this comparator
     */
    @FunctionalInterface
    interface SerializableComparator extends Comparator, Serializable {
    }
}