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/* * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved. * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. * * * * * * * * * * * * * * * * * * * * */ 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> { INSTANCE; @Override public int compare(Comparable c1, Comparable c2) { return c1.compareTo(c2); } @Override public Comparator> reversed() { return Comparator.reverseOrder(); } } /** * Null-friendly comparators */ final static class NullComparator implements Comparator, Serializable { private static final long serialVersionUID = -7569533591570686392L; private final boolean nullFirst; // if null, non-null Ts are considered equal private final Comparator real; @SuppressWarnings("unchecked") NullComparator(boolean nullFirst, Comparator super T> real) { this.nullFirst = nullFirst; this.real = (Comparator) 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 thenComparing(Comparator super T> other) { Objects.requireNonNull(other); return new NullComparator<>(nullFirst, real == null ? other : real.thenComparing(other)); } @Override public Comparator reversed() { return new NullComparator<>(!nullFirst, real == null ? null : real.reversed()); } } }