/*
 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package java.util;

import java.io.Serializable;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.ToDoubleFunction;
import java.util.function.ToIntFunction;
import java.util.function.ToLongFunction;

/**
 * Package private supporting class for {@link Comparator}.
 */
class Comparators {
 private Comparators() {
 throw new AssertionError("no instances");
 }

 /**
 * Compares {@link Comparable} objects in natural order.
 *
 * @see Comparable
 */
 enum NaturalOrderComparator implements Comparator<Comparable<Object>> {
 INSTANCE;

 @Override
 public int compare(Comparable<Object> c1, Comparable<Object> c2) {
 return c1.compareTo(c2);
 }

 @Override
 public Comparator<Comparable<Object>> reversed() {
 return Comparator.reverseOrder();
 }
 }

 /**
 * Null-friendly comparators
 */
 static final class NullComparator<T> implements Comparator<T>, Serializable {
 private static final long serialVersionUID = -7569533591570686392L;
 private final boolean nullFirst;
 // if null, non-null Ts are considered equal
 private final Comparator<T> real;

 @SuppressWarnings("unchecked")
 NullComparator(boolean nullFirst, Comparator<? super T> real) {
 this.nullFirst = nullFirst;
 this.real = (Comparator<T>) real;
 }

 @Override
 public int compare(T a, T b) {
 if (a == null) {
 return (b == null) ? 0 : (nullFirst ? -1 : 1);
 } else if (b == null) {
 return nullFirst ? 1: -1;
 } else {
 return (real == null) ? 0 : real.compare(a, b);
 }
 }

 @Override
 public Comparator<T> thenComparing(Comparator<? super T> other) {
 Objects.requireNonNull(other);
 return new NullComparator<>(nullFirst, real == null ? other : real.thenComparing(other));
 }

 @Override
 public Comparator<T> reversed() {
 return new NullComparator<>(!nullFirst, real == null ? null : real.reversed());
 }
 }
}