101 lines
3.4 KiB
Java
101 lines
3.4 KiB
Java
/*
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* Copyright (c) 2012, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.util;
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import java.io.Serializable;
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import java.util.function.BinaryOperator;
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import java.util.function.Function;
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import java.util.function.ToDoubleFunction;
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import java.util.function.ToIntFunction;
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import java.util.function.ToLongFunction;
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/**
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* Package private supporting class for {@link Comparator}.
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*/
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class Comparators {
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private Comparators() {
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throw new AssertionError("no instances");
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}
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/**
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* Compares {@link Comparable} objects in natural order.
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*
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* @see Comparable
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*/
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enum NaturalOrderComparator implements Comparator<Comparable<Object>> {
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INSTANCE;
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@Override
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public int compare(Comparable<Object> c1, Comparable<Object> c2) {
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return c1.compareTo(c2);
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}
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@Override
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public Comparator<Comparable<Object>> reversed() {
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return Comparator.reverseOrder();
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}
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}
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/**
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* Null-friendly comparators
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*/
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static final class NullComparator<T> implements Comparator<T>, Serializable {
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@java.io.Serial
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private static final long serialVersionUID = -7569533591570686392L;
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private final boolean nullFirst;
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// if null, non-null Ts are considered equal
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@SuppressWarnings("serial") // Not statically typed as Serializable
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private final Comparator<T> real;
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@SuppressWarnings("unchecked")
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NullComparator(boolean nullFirst, Comparator<? super T> real) {
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this.nullFirst = nullFirst;
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this.real = (Comparator<T>) real;
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}
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@Override
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public int compare(T a, T b) {
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if (a == null) {
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return (b == null) ? 0 : (nullFirst ? -1 : 1);
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} else if (b == null) {
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return nullFirst ? 1: -1;
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} else {
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return (real == null) ? 0 : real.compare(a, b);
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}
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}
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@Override
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public Comparator<T> thenComparing(Comparator<? super T> other) {
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Objects.requireNonNull(other);
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return new NullComparator<>(nullFirst, real == null ? other : real.thenComparing(other));
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}
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@Override
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public Comparator<T> reversed() {
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return new NullComparator<>(!nullFirst, real == null ? null : real.reversed());
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}
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}
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}
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