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/*
 * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
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package java.lang.constant;

import java.lang.Enum.EnumDesc;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.invoke.VarHandle.VarHandleDesc;

/**
 * A nominal descriptor for a loadable
 * constant value, as defined in JVMS 4.4. Such a descriptor can be resolved via
 * {@link ConstantDesc#resolveConstantDesc(MethodHandles.Lookup)} to yield the
 * constant value itself.
 *
 * 

Class names in a nominal descriptor, like class names in the constant pool * of a classfile, must be interpreted with respect to a particular class * loader, which is not part of the nominal descriptor. * *

Static constants that are expressible natively in the constant pool ({@link String}, * {@link Integer}, {@link Long}, {@link Float}, and {@link Double}) implement * {@link ConstantDesc}, and serve as nominal descriptors for themselves. * Native linkable constants ({@link Class}, {@link MethodType}, and * {@link MethodHandle}) have counterpart {@linkplain ConstantDesc} types: * {@link ClassDesc}, {@link MethodTypeDesc}, and {@link MethodHandleDesc}. * Other constants are represented by subtypes of {@link DynamicConstantDesc}. * *

APIs that perform generation or parsing of bytecode are encouraged to use * {@linkplain ConstantDesc} to describe the operand of an {@code ldc} instruction * (including dynamic constants), the static bootstrap arguments of * dynamic constants and {@code invokedynamic} instructions, and other * bytecodes or classfile structures that make use of the constant pool. * *

Constants describing various common constants (such as {@link ClassDesc} * instances for platform types) can be found in {@link ConstantDescs}. * *

Implementations of {@linkplain ConstantDesc} should be immutable * and their behavior should not rely on object identity. * *

Non-platform classes should not implement {@linkplain ConstantDesc} directly. * Instead, they should extend {@link DynamicConstantDesc} (as {@link EnumDesc} * and {@link VarHandleDesc} do.) * *

Nominal descriptors should be compared using the * {@link Object#equals(Object)} method. There is no guarantee that any * particular entity will always be represented by the same descriptor instance. * * @see Constable * @see ConstantDescs * * @jvms 4.4 The Constant Pool * * @since 12 */ public sealed interface ConstantDesc permits ClassDesc, MethodHandleDesc, MethodTypeDesc, Double, DynamicConstantDesc, Float, Integer, Long, String { /** * Resolves this descriptor reflectively, emulating the resolution behavior * of JVMS 5.4.3 and the access control behavior of JVMS 5.4.4. The resolution * and access control context is provided by the {@link MethodHandles.Lookup} * parameter. No caching of the resulting value is performed. * * @param lookup The {@link MethodHandles.Lookup} to provide name resolution * and access control context * @return the resolved constant value * @throws ReflectiveOperationException if a class, method, or field * could not be reflectively resolved in the course of resolution * @throws LinkageError if a linkage error occurs * * @apiNote {@linkplain MethodTypeDesc} can represent method type descriptors * that are not representable by {@linkplain MethodType}, such as methods with * more than 255 parameter slots, so attempts to resolve these may result in errors. * * @jvms 5.4.3 Resolution * @jvms 5.4.4 Access Control */ Object resolveConstantDesc(MethodHandles.Lookup lookup) throws ReflectiveOperationException; }





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