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 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 must be value-based.

Since:

12

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method	Description
ConstantDesc[]	bootstrapArgs()	Returns the bootstrap arguments for this constant
java.util.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.
boolean	equals(Object o)	Compares the specified object with this descriptor for equality.
int	hashCode()	Returns a hash code value for the object.
static <T> DynamicConstantDesc<T>	of(DirectMethodHandleDesc bootstrapMethod)	Return 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)	Return 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)	Return 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)	Return a nominal descriptor for a dynamic constant.
T	resolveConstantDesc(MethodHandles.Lookup lookup)	Resolve 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 string representation of the object.

Methods inherited from class java.lang.Object

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

Constructor Detail

DynamicConstantDesc

protected DynamicConstantDesc(DirectMethodHandleDesc bootstrapMethod,
                              String constantName,
                              ClassDesc constantType,
                              ConstantDesc... bootstrapArgs)

Create a nominal descriptor for a dynamic constant.

Parameters:

bootstrapMethod - a DirectMethodHandleDescImpl 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 DirectMethodHandleDescImpl describing the type that would appear in the NameAndType operand of the LDC for this constant

bootstrapArgs - ConstantDescs 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

Method Detail

ofCanonical

public static <T> ConstantDesc ofCanonical(DirectMethodHandleDesc bootstrapMethod,
                                           String constantName,
                                           ClassDesc constantType,
                                           ConstantDesc[] bootstrapArgs)

Return 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 produces 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 DirectMethodHandleDescImpl describing the type that would appear in the NameAndType operand of the LDC for this constant

bootstrapArgs - ConstantDescs 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

ofNamed

public static <T> DynamicConstantDesc<T> ofNamed(DirectMethodHandleDesc bootstrapMethod,
                                                 String constantName,
                                                 ClassDesc constantType,
                                                 ConstantDesc... bootstrapArgs)

Return a nominal descriptor for a dynamic constant.

Type Parameters:

T - the type of the dynamic constant

Parameters:

bootstrapMethod - a DirectMethodHandleDescImpl 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 - ConstantDescs 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

of

public static <T> DynamicConstantDesc<T> of(DirectMethodHandleDesc bootstrapMethod,
                                            ConstantDesc... bootstrapArgs)

Return 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 DirectMethodHandleDescImpl describing the bootstrap method for the constant

bootstrapArgs - ConstantDescs 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

of

public static <T> DynamicConstantDesc<T> of(DirectMethodHandleDesc bootstrapMethod)

Return 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 DirectMethodHandleDescImpl 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 java.util.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

Resolve 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 equals to this DynamicConstantDesc.

See Also:

Object.hashCode(), HashMap

hashCode

public final int hashCode()

Description copied from class: Object

Returns a hash code value for the 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(Object) 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 Object.equals(java.lang.Object) 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.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (The hashCode may or may not be implemented as some function of an object's memory address at some point in time.)

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()

Description copied from class: Object

Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

 getClass().getName() + '@' + Integer.toHexString(hashCode())
 

Overrides:

toString in class Object

Returns:

a string representation of the object.