410 lines
16 KiB
Java
410 lines
16 KiB
Java
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/*
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* Copyright (C) 2014 The Android Open Source Project
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* Copyright (c) 2003, 2020, 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.lang;
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import java.io.IOException;
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import java.io.InvalidObjectException;
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import java.io.ObjectInputStream;
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import java.io.ObjectStreamException;
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import java.io.Serializable;
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import java.lang.constant.ClassDesc;
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import java.lang.constant.Constable;
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import java.lang.constant.ConstantDescs;
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import java.lang.constant.DynamicConstantDesc;
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import java.lang.invoke.MethodHandles;
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import java.util.Optional;
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import java.lang.reflect.InvocationTargetException;
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import java.lang.reflect.Method;
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import libcore.util.BasicLruCache;
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import static java.util.Objects.requireNonNull;
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/**
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* This is the common base class of all Java language enumeration classes.
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*
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* More information about enums, including descriptions of the
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* implicitly declared methods synthesized by the compiler, can be
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* found in section {@jls 8.9} of <cite>The Java Language
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* Specification</cite>.
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*
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* Enumeration classes are all serializable and receive special handling
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* by the serialization mechanism. The serialized representation used
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* for enum constants cannot be customized. Declarations of methods
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* and fields that would otherwise interact with serialization are
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* ignored, including {@code serialVersionUID}; see the <cite>Java
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* Object Serialization Specification</cite> for details.
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*
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* <p> Note that when using an enumeration type as the type of a set
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* or as the type of the keys in a map, specialized and efficient
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* {@linkplain java.util.EnumSet set} and {@linkplain
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* java.util.EnumMap map} implementations are available.
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*
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* @param <E> The type of the enum subclass
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* @serial exclude
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* @author Josh Bloch
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* @author Neal Gafter
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* @see Class#getEnumConstants()
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* @see java.util.EnumSet
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* @see java.util.EnumMap
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* @jls 8.9 Enum Classes
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* @jls 8.9.3 Enum Members
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* @since 1.5
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*/
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@SuppressWarnings("serial") // No serialVersionUID needed due to
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// special-casing of enum classes.
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public abstract class Enum<E extends Enum<E>>
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implements Constable, Comparable<E>, Serializable {
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/**
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* The name of this enum constant, as declared in the enum declaration.
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* Most programmers should use the {@link #toString} method rather than
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* accessing this field.
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*/
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private final String name;
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/**
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* Returns the name of this enum constant, exactly as declared in its
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* enum declaration.
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*
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* <b>Most programmers should use the {@link #toString} method in
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* preference to this one, as the toString method may return
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* a more user-friendly name.</b> This method is designed primarily for
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* use in specialized situations where correctness depends on getting the
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* exact name, which will not vary from release to release.
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*
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* @return the name of this enum constant
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*/
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public final String name() {
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return name;
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}
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/**
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* The ordinal of this enumeration constant (its position
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* in the enum declaration, where the initial constant is assigned
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* an ordinal of zero).
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*
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* Most programmers will have no use for this field. It is designed
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* for use by sophisticated enum-based data structures, such as
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* {@link java.util.EnumSet} and {@link java.util.EnumMap}.
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*/
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private final int ordinal;
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/**
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* Returns the ordinal of this enumeration constant (its position
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* in its enum declaration, where the initial constant is assigned
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* an ordinal of zero).
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*
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* Most programmers will have no use for this method. It is
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* designed for use by sophisticated enum-based data structures, such
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* as {@link java.util.EnumSet} and {@link java.util.EnumMap}.
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*
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* @return the ordinal of this enumeration constant
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*/
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public final int ordinal() {
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return ordinal;
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}
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/**
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* Sole constructor. Programmers cannot invoke this constructor.
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* It is for use by code emitted by the compiler in response to
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* enum class declarations.
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*
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* @param name - The name of this enum constant, which is the identifier
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* used to declare it.
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* @param ordinal - The ordinal of this enumeration constant (its position
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* in the enum declaration, where the initial constant is assigned
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* an ordinal of zero).
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*/
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protected Enum(String name, int ordinal) {
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this.name = name;
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this.ordinal = ordinal;
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}
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/**
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* Returns the name of this enum constant, as contained in the
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* declaration. This method may be overridden, though it typically
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* isn't necessary or desirable. An enum class should override this
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* method when a more "programmer-friendly" string form exists.
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*
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* @return the name of this enum constant
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*/
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public String toString() {
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return name;
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}
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/**
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* Returns true if the specified object is equal to this
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* enum constant.
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*
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* @param other the object to be compared for equality with this object.
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* @return true if the specified object is equal to this
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* enum constant.
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*/
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public final boolean equals(Object other) {
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return this==other;
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}
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/**
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* Returns a hash code for this enum constant.
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*
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* @return a hash code for this enum constant.
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*/
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public final int hashCode() {
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return super.hashCode();
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}
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/**
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* Throws CloneNotSupportedException. This guarantees that enums
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* are never cloned, which is necessary to preserve their "singleton"
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* status.
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*
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* @return (never returns)
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*/
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protected final Object clone() throws CloneNotSupportedException {
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throw new CloneNotSupportedException();
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}
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/**
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* Compares this enum with the specified object for order. Returns a
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* negative integer, zero, or a positive integer as this object is less
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* than, equal to, or greater than the specified object.
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*
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* Enum constants are only comparable to other enum constants of the
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* same enum type. The natural order implemented by this
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* method is the order in which the constants are declared.
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*/
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public final int compareTo(E o) {
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Enum<?> other = (Enum<?>)o;
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Enum<E> self = this;
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if (self.getClass() != other.getClass() && // optimization
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self.getDeclaringClass() != other.getDeclaringClass())
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throw new ClassCastException();
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return self.ordinal - other.ordinal;
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}
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/**
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* Returns the Class object corresponding to this enum constant's
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* enum type. Two enum constants e1 and e2 are of the
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* same enum type if and only if
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* e1.getDeclaringClass() == e2.getDeclaringClass().
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* (The value returned by this method may differ from the one returned
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* by the {@link Object#getClass} method for enum constants with
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* constant-specific class bodies.)
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*
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* @return the Class object corresponding to this enum constant's
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* enum type
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*/
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@SuppressWarnings("unchecked")
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public final Class<E> getDeclaringClass() {
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Class<?> clazz = getClass();
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Class<?> zuper = clazz.getSuperclass();
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return (zuper == Enum.class) ? (Class<E>)clazz : (Class<E>)zuper;
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}
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/**
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* Returns an enum descriptor {@code EnumDesc} for this instance, if one can be
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* constructed, or an empty {@link Optional} if one cannot be.
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*
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* @return An {@link Optional} containing the resulting nominal descriptor,
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* or an empty {@link Optional} if one cannot be constructed.
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* @since 12
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* @hide
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*/
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@Override
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public final Optional<EnumDesc<E>> describeConstable() {
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return getDeclaringClass()
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.describeConstable()
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.map(c -> EnumDesc.of(c, name));
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}
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/**
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* Returns the enum constant of the specified enum class with the
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* specified name. The name must match exactly an identifier used
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* to declare an enum constant in this class. (Extraneous whitespace
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* characters are not permitted.)
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*
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* <p>Note that for a particular enum class {@code T}, the
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* implicitly declared {@code public static T valueOf(String)}
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* method on that enum may be used instead of this method to map
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* from a name to the corresponding enum constant. All the
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* constants of an enum class can be obtained by calling the
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* implicit {@code public static T[] values()} method of that
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* class.
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*
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* @param <T> The enum class whose constant is to be returned
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* @param enumClass the {@code Class} object of the enum class from which
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* to return a constant
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* @param name the name of the constant to return
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* @return the enum constant of the specified enum class with the
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* specified name
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* @throws IllegalArgumentException if the specified enum class has
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* no constant with the specified name, or the specified
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* class object does not represent an enum class
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* @throws NullPointerException if {@code enumClass} or {@code name}
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* is null
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* @since 1.5
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*/
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// BEGIN Android-changed: Use a static BasicLruCache mapping Enum class -> Enum instance array.
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// This change was made to fix a performance regression. See b/4087759 and b/109791362 for more
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// background information.
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/*
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public static <T extends Enum<T>> T valueOf(Class<T> enumClass,
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String name) {
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T result = enumClass.enumConstantDirectory().get(name);
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if (result != null)
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return result;
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if (name == null)
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throw new NullPointerException("Name is null");
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*/
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public static <T extends Enum<T>> T valueOf(Class<T> enumClass,
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String name) {
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requireNonNull(enumClass, "enumClass == null");
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requireNonNull(name, "name == null");
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T[] values = getSharedConstants(enumClass);
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if (values == null) {
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throw new IllegalArgumentException(enumClass.toString() + " is not an enum type.");
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}
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// Iterate backwards through the array to retain historic Android behavior in the
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// unexpected / likely invalid case where there are multiple values with the same name.
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for (int i = values.length - 1; i >= 0; --i) {
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T value = values[i];
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if (name.equals(value.name())) {
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return value;
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}
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}
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throw new IllegalArgumentException(
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"No enum constant " + enumClass.getCanonicalName() + "." + name);
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}
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private static Object[] enumValues(Class<? extends Enum> clazz) {
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if (!clazz.isEnum()) {
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// Either clazz is Enum.class itself, or it is not an enum class and the method was
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// called unsafely e.g. using an unchecked cast or via reflection.
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return null;
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}
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try {
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Method valueMethod = clazz.getDeclaredMethod("values");
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return (Object[]) valueMethod.invoke(null);
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} catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
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throw new RuntimeException(e);
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}
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}
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private static final BasicLruCache<Class<? extends Enum>, Object[]> sharedConstantsCache
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= new BasicLruCache<Class<? extends Enum>, Object[]>(64) {
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@Override protected Object[] create(Class<? extends Enum> enumType) {
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return enumValues(enumType);
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}
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};
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/**
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* Returns a shared, mutable array containing the constants of this enum. It
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* is an error to modify the returned array.
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*
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* @hide
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*/
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@SuppressWarnings("unchecked") // the cache always returns the type matching enumType
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public static <T extends Enum<T>> T[] getSharedConstants(Class<T> enumType) {
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return (T[]) sharedConstantsCache.get(enumType);
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}
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// END Android-changed: Use a static BasicLruCache mapping Enum class -> Enum instance array.
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/**
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* enum classes cannot have finalize methods.
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*/
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@SuppressWarnings("deprecation")
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protected final void finalize() { }
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/**
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* prevent default deserialization
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*/
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@java.io.Serial
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private void readObject(ObjectInputStream in) throws IOException,
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ClassNotFoundException {
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throw new InvalidObjectException("can't deserialize enum");
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}
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@java.io.Serial
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private void readObjectNoData() throws ObjectStreamException {
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throw new InvalidObjectException("can't deserialize enum");
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}
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// Android-changed: Hide EnumDesc API until master switches away from Android U dev. b/270028670
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/**
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* A <a href="{@docRoot}/java.base/java/lang/constant/package-summary.html#nominal">nominal descriptor</a> for an
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* {@code enum} constant.
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*
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* @param <E> the type of the enum constant
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*
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* @since 12
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* @hide
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*/
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public static final class EnumDesc<E extends Enum<E>>
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extends DynamicConstantDesc<E> {
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|
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/**
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* Constructs a nominal descriptor for the specified {@code enum} class and name.
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*
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* @param constantClass a {@link ClassDesc} describing the {@code enum} class
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* @param constantName the unqualified name of the enum constant
|
||
|
|
* @throws NullPointerException if any argument is null
|
||
|
|
* @jvms 4.2.2 Unqualified Names
|
||
|
|
*/
|
||
|
|
private EnumDesc(ClassDesc constantClass, String constantName) {
|
||
|
|
super(ConstantDescs.BSM_ENUM_CONSTANT, requireNonNull(constantName), requireNonNull(constantClass));
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Returns a nominal descriptor for the specified {@code enum} class and name
|
||
|
|
*
|
||
|
|
* @param <E> the type of the enum constant
|
||
|
|
* @param enumClass a {@link ClassDesc} describing the {@code enum} class
|
||
|
|
* @param constantName the unqualified name of the enum constant
|
||
|
|
* @return the nominal descriptor
|
||
|
|
* @throws NullPointerException if any argument is null
|
||
|
|
* @jvms 4.2.2 Unqualified Names
|
||
|
|
* @since 12
|
||
|
|
*/
|
||
|
|
public static<E extends Enum<E>> EnumDesc<E> of(ClassDesc enumClass,
|
||
|
|
String constantName) {
|
||
|
|
return new EnumDesc<>(enumClass, constantName);
|
||
|
|
}
|
||
|
|
|
||
|
|
@Override
|
||
|
|
@SuppressWarnings("unchecked")
|
||
|
|
public E resolveConstantDesc(MethodHandles.Lookup lookup)
|
||
|
|
throws ReflectiveOperationException {
|
||
|
|
return Enum.valueOf((Class<E>) constantType().resolveConstantDesc(lookup), constantName());
|
||
|
|
}
|
||
|
|
|
||
|
|
@Override
|
||
|
|
public String toString() {
|
||
|
|
return String.format("EnumDesc[%s.%s]", constantType().displayName(), constantName());
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|