DynamicConstantDesc (Java SE 22 & JDK 22)
Description: declaration: module: java.base, package: java.lang.constant, class: DynamicConstantDesc
Keywords: java.lang.constant.DynamicConstantDesc class

Module java.base
Package java.lang.constant

# Class DynamicConstantDesc<T>

java.lang.Object
java.lang.constant.DynamicConstantDesc<T>

Type Parameters:
  `T` - the type of the dynamic constant

All Implemented Interfaces:
  `ConstantDesc`

Direct Known Subclasses:
  `Enum.EnumDesc`, `VarHandle.VarHandleDesc`

public abstract non-sealed class DynamicConstantDesc<T> extends Object implements ConstantDesc
A nominal descriptor for a dynamic constant (one described in the constant pool with `Constant_Dynamic_info`.)

Concrete subtypes of DynamicConstantDesc should be immutable and their behavior should not rely on object identity.

Since:
  12

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `DynamicConstantDesc(DirectMethodHandleDesc bootstrapMethod, String constantName, ClassDesc constantType, ConstantDesc... bootstrapArgs)`
  Creates a nominal descriptor for a dynamic constant.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `ConstantDesc[]`
  `bootstrapArgs()`
  Returns the bootstrap arguments for this constant.
  `List<ConstantDesc>`
  `bootstrapArgsList()`
  Returns the bootstrap arguments for this constant as an immutable `List`.
  `DirectMethodHandleDesc`
  `bootstrapMethod()`
  Returns a `MethodHandleDesc` describing the bootstrap method for this constant.
  `String`
  `constantName()`
  Returns the name that would appear in the `NameAndType` operand of the `LDC` for this constant.
  `ClassDesc`
  `constantType()`
  Returns a `ClassDesc` describing the type that would appear in the `NameAndType` operand of the `LDC` for this constant.
  `final boolean`
  `equals(Object o)`
  Compares the specified object with this descriptor for equality.
  `final int`
  `hashCode()`
  Returns a hash code value for this object.
  `static <T> DynamicConstantDesc<T>`
  `of(DirectMethodHandleDesc bootstrapMethod)`
  Returns a nominal descriptor for a dynamic constant whose bootstrap has no static arguments, whose name parameter is `ConstantDescs.DEFAULT_NAME`, and whose type parameter is always the same as the bootstrap method return type.
  `static <T> DynamicConstantDesc<T>`
  `of(DirectMethodHandleDesc bootstrapMethod, ConstantDesc... bootstrapArgs)`
  Returns a nominal descriptor for a dynamic constant whose name parameter is `ConstantDescs.DEFAULT_NAME`, and whose type parameter is always the same as the bootstrap method return type.
  `static <T> ConstantDesc`
  `ofCanonical(DirectMethodHandleDesc bootstrapMethod, String constantName, ClassDesc constantType, ConstantDesc[] bootstrapArgs)`
  Returns a nominal descriptor for a dynamic constant, transforming it into a more specific type if the constant bootstrap is a well-known one and a more specific nominal descriptor type (e.g., ClassDesc) is available.
  `static <T> DynamicConstantDesc<T>`
  `ofNamed(DirectMethodHandleDesc bootstrapMethod, String constantName, ClassDesc constantType, ConstantDesc... bootstrapArgs)`
  Returns a nominal descriptor for a dynamic constant.
  `T`
  `resolveConstantDesc(MethodHandles.Lookup lookup)`
  Resolves this descriptor reflectively, emulating the resolution behavior of JVMS 5.4.3 and the access control behavior of JVMS 5.4.4.
  `String`
  `toString()`
  Returns a compact textual description of this constant description, including the bootstrap method, the constant name and type, and the static bootstrap arguments.

  ### Methods declared in class java.lang.Object

  `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### DynamicConstantDesc

    protected DynamicConstantDesc(DirectMethodHandleDesc bootstrapMethod, String constantName, ClassDesc constantType, ConstantDesc... bootstrapArgs)
    Creates a nominal descriptor for a dynamic constant.
    Parameters:
      `bootstrapMethod` - a `DirectMethodHandleDesc` describing the bootstrap method for the constant
      `constantName` - The unqualified name that would appear in the `NameAndType` operand of the `LDC` for this constant
      `constantType` - a `ClassDesc` describing the type that would appear in the `NameAndType` operand of the `LDC` for this constant
      `bootstrapArgs` - `ConstantDesc`s describing the static arguments to the bootstrap, that would appear in the `BootstrapMethods` attribute
    Throws:
      `NullPointerException` - if any argument is null
      `IllegalArgumentException` - if the `name` has the incorrect format
    See Java Virtual Machine Specification:
      4.2.2 Unqualified Names

- ## Method Details

  - ### ofCanonical

    public static <T> ConstantDesc ofCanonical(DirectMethodHandleDesc bootstrapMethod, String constantName, ClassDesc constantType, ConstantDesc[] bootstrapArgs)
    Returns a nominal descriptor for a dynamic constant, transforming it into a more specific type if the constant bootstrap is a well-known one and a more specific nominal descriptor type (e.g., ClassDesc) is available.

    Classes whose `Constable.describeConstable()` method produce a DynamicConstantDesc with a well-known bootstrap including `Class` (for instances describing primitive types), `Enum`, and `VarHandle`.

    Bytecode-reading APIs that process the constant pool and wish to expose entries as `ConstantDesc` to their callers should generally use this method in preference to `ofNamed(DirectMethodHandleDesc, String, ClassDesc, ConstantDesc...)` because this may result in a more specific type that can be provided to callers.

    Type Parameters:
      `T` - the type of the dynamic constant
    Parameters:
      `bootstrapMethod` - a `DirectMethodHandleDesc` describing the bootstrap method for the constant
      `constantName` - The unqualified name that would appear in the `NameAndType` operand of the `LDC` for this constant
      `constantType` - a `ClassDesc` describing the type that would appear in the `NameAndType` operand of the `LDC` for this constant
      `bootstrapArgs` - `ConstantDesc`s describing the static arguments to the bootstrap, that would appear in the `BootstrapMethods` attribute
    Returns:
      the nominal descriptor
    Throws:
      `NullPointerException` - if any argument is null
      `IllegalArgumentException` - if the `name` has the incorrect format
    See Java Virtual Machine Specification:
      4.2.2 Unqualified Names

  - ### ofNamed

    public static <T> DynamicConstantDesc<T> ofNamed(DirectMethodHandleDesc bootstrapMethod, String constantName, ClassDesc constantType, ConstantDesc... bootstrapArgs)
    Returns a nominal descriptor for a dynamic constant.
    Type Parameters:
      `T` - the type of the dynamic constant
    Parameters:
      `bootstrapMethod` - a `DirectMethodHandleDesc` describing the bootstrap method for the constant
      `constantName` - The unqualified name that would appear in the `NameAndType` operand of the `LDC` for this constant
      `constantType` - a `ClassDesc` describing the type that would appear in the `NameAndType` operand of the `LDC` for this constant
      `bootstrapArgs` - `ConstantDesc`s describing the static arguments to the bootstrap, that would appear in the `BootstrapMethods` attribute
    Returns:
      the nominal descriptor
    Throws:
      `NullPointerException` - if any argument is null
      `IllegalArgumentException` - if the `name` has the incorrect format
    See Java Virtual Machine Specification:
      4.2.2 Unqualified Names

  - ### of

    public static <T> DynamicConstantDesc<T> of(DirectMethodHandleDesc bootstrapMethod, ConstantDesc... bootstrapArgs)
    Returns a nominal descriptor for a dynamic constant whose name parameter is `ConstantDescs.DEFAULT_NAME`, and whose type parameter is always the same as the bootstrap method return type.
    Type Parameters:
      `T` - the type of the dynamic constant
    Parameters:
      `bootstrapMethod` - a `DirectMethodHandleDesc` describing the bootstrap method for the constant
      `bootstrapArgs` - `ConstantDesc`s describing the static arguments to the bootstrap, that would appear in the `BootstrapMethods` attribute
    Returns:
      the nominal descriptor
    Throws:
      `NullPointerException` - if any argument is null
    See Java Virtual Machine Specification:
      4.2.2 Unqualified Names

  - ### of

    public static <T> DynamicConstantDesc<T> of(DirectMethodHandleDesc bootstrapMethod)
    Returns a nominal descriptor for a dynamic constant whose bootstrap has no static arguments, whose name parameter is `ConstantDescs.DEFAULT_NAME`, and whose type parameter is always the same as the bootstrap method return type.
    Type Parameters:
      `T` - the type of the dynamic constant
    Parameters:
      `bootstrapMethod` - a `DirectMethodHandleDesc` describing the bootstrap method for the constant
    Returns:
      the nominal descriptor
    Throws:
      `NullPointerException` - if any argument is null

  - ### constantName

    public String constantName()
    Returns the name that would appear in the `NameAndType` operand of the `LDC` for this constant.
    Returns:
      the constant name

  - ### constantType

    public ClassDesc constantType()
    Returns a `ClassDesc` describing the type that would appear in the `NameAndType` operand of the `LDC` for this constant.
    Returns:
      the constant type

  - ### bootstrapMethod

    public DirectMethodHandleDesc bootstrapMethod()
    Returns a `MethodHandleDesc` describing the bootstrap method for this constant.
    Returns:
      the bootstrap method

  - ### bootstrapArgs

    public ConstantDesc[] bootstrapArgs()
    Returns the bootstrap arguments for this constant.
    Returns:
      the bootstrap arguments

  - ### bootstrapArgsList

    public List<ConstantDesc> bootstrapArgsList()
    Returns the bootstrap arguments for this constant as an immutable `List`.
    Returns:
      a `List` of the bootstrap arguments

  - ### resolveConstantDesc

    public T resolveConstantDesc(MethodHandles.Lookup lookup) throws ReflectiveOperationException
    Description copied from interface: `ConstantDesc`
    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.
    Specified by:
      `resolveConstantDesc` in interface `ConstantDesc`
    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

  - ### equals

    public final boolean equals(Object o)
    Compares the specified object with this descriptor for equality. Returns `true` if and only if the specified object is also a DynamicConstantDesc, and both descriptors have equal bootstrap methods, bootstrap argument lists, constant name, and constant type.
    Overrides:
      `equals` in class `Object`
    Parameters:
      `o` - the `DynamicConstantDesc` to compare to this `DynamicConstantDesc`
    Returns:
      `true` if the specified `DynamicConstantDesc` is equal to this `DynamicConstantDesc`.
    See Also:
      - `Object.hashCode()`
      - `HashMap`

  - ### hashCode

    public final int hashCode()
    Description copied from class: `Object`
    Returns a hash code value for this object. This method is supported for the benefit of hash tables such as those provided by `HashMap`.

    The general contract of `hashCode` is:

    - Whenever it is invoked on the same object more than once during an execution of a Java application, the `hashCode` method must consistently return the same integer, provided no information used in `equals` comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
    - If two objects are equal according to the `equals` method, then calling the `hashCode` method on each of the two objects must produce the same integer result.
    - It is not required that if two objects are unequal according to the `equals` method, then calling the `hashCode` method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
    Overrides:
      `hashCode` in class `Object`
    Returns:
      a hash code value for this object
    See Also:
      - `Object.equals(java.lang.Object)`
      - `System.identityHashCode(java.lang.Object)`

  - ### toString

    public String toString()
    Returns a compact textual description of this constant description, including the bootstrap method, the constant name and type, and the static bootstrap arguments.
    Overrides:
      `toString` in class `Object`
    Returns:
      A compact textual description of this call site descriptor