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Showing content from https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/constant/ConstantDesc.html below:

ConstantDesc (Java SE 21 & JDK 21)

All Known Subinterfaces:

ClassDesc, DirectMethodHandleDesc, MethodHandleDesc, MethodTypeDesc

A

for a loadable constant value, as defined in JVMS

. Such a descriptor can be resolved via

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 (String, Integer, Long, Float, and Double) implement ConstantDesc, and serve as nominal descriptors for themselves. Native linkable constants (Class, MethodType, and MethodHandle) have counterpart ConstantDesc types: ClassDesc, MethodTypeDesc, and MethodHandleDesc. Other constants are represented by subtypes of DynamicConstantDesc.

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

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

Implementations of ConstantDesc should be immutable and their behavior should not rely on object identity.

Non-platform classes should not implement ConstantDesc directly. Instead, they should extend DynamicConstantDesc (as Enum.EnumDesc and VarHandle.VarHandleDesc do.)

Nominal descriptors should be compared using the Object.equals(Object) method. There is no guarantee that any particular entity will always be represented by the same descriptor instance.

See Java Virtual Machine Specification:

4.4 The Constant Pool

Sealed Class Hierarchy Graph:

Since:

12

See Also:

• Constable
• ConstantDescs

• Method Summary

  Resolves this descriptor reflectively, emulating the resolution behavior of JVMS

  5.4.3

  and the access control behavior of JVMS

  5.4.4

  .

• Method Details
  • resolveConstantDesc

    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

    MethodHandles.Lookup

    parameter. No caching of the resulting value is performed.

    API Note:

    Some constant descriptors, such as MethodTypeDesc, can represent a value that is not representable by run-time entities. Attempts to resolve these may result in errors.

    Parameters:

    lookup - The MethodHandles.Lookup to provide name resolution and access control context

    Returns:

    the resolved constant value

    Throws:

    ReflectiveOperationException - if a class, method, or field could not be reflectively resolved in the course of resolution

    LinkageError - if a linkage error occurs

    See Java Virtual Machine Specification:

    5.4.3 Resolution
    5.4.4 Access Control
    

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