Top Description Constructors Methods
java.lang.invoke

public final Class ConstantBootstraps

extends Object
Class Inheritance
Imports
sun.invoke.util.Wrapper
Bootstrap methods for dynamically-computed constants.

The bootstrap methods in this class will throw a NullPointerException for any reference argument that is null, unless the argument is specified to be unused or specified to accept a null value.

Since
11

Constructor Summary

AccessConstructor and Description
private
ConstantBootstraps()

Do not call.

Method Summary

Modifier and TypeMethod and Description
public static VarHandle

Returns:

the VarHandle
arrayVarHandle(MethodHandles.Lookup
the lookup context describing the class performing the operation (normally stacked by the JVM)
lookup, String
unused
name, Class<VarHandle>
the required result type (must be Class<VarHandle>)
type, Class<?>
the type of the array
arrayClass)

Finds a VarHandle for an array type.

public static <
The enum type for which a constant value is to be returned
E extends Enum<E>> E

Returns:

the enum constant of the specified enum type with the specified name
enumConstant(MethodHandles.Lookup
the lookup context describing the class performing the operation (normally stacked by the JVM)
lookup, String
the name of the constant to return, which must exactly match an enum constant in the specified type.
name, Class<E>
the Class object describing the enum type for which a constant is to be returned
type)

Returns an enum constant of the type specified by type with the name specified by name.

public static Object

Returns:

the converted value
explicitCast(MethodHandles.Lookup
unused
lookup, String
unused
name, Class<?>
the destination type of the conversion
dstType, Object
the value to be converted
value)

Applies a conversion from a source type to a destination type.

public static VarHandle

Returns:

the VarHandle
fieldVarHandle(MethodHandles.Lookup
the lookup context describing the class performing the operation (normally stacked by the JVM)
lookup, String
the name of the field
name, Class<VarHandle>
the required result type (must be Class<VarHandle>)
type, Class<?>
the class in which the field is declared
declaringClass, Class<?>
the type of the field
fieldType)

Finds a VarHandle for an instance field.

public static Object

Returns:

the value of the field
getStaticFinal(MethodHandles.Lookup
the lookup context describing the class performing the operation (normally stacked by the JVM)
lookup, String
the name of the field
name, Class<?>
the type of the field
type, Class<?>
the class in which the field is declared
declaringClass)

Returns the value of a static final field.

public static Object

Returns:

the value of the field
getStaticFinal(MethodHandles.Lookup
the lookup context describing the class performing the operation (normally stacked by the JVM)
lookup, String
the name of the field
name, Class<?>
the type of the field
type)

Returns the value of a static final field declared in the class which is the same as the field's type (or, for primitive-valued fields, declared in the wrapper class.) This is a simplified form of getStaticFinal(MethodHandles.Lookup, String, Class, Class) for the case where a class declares distinguished constant instances of itself.

public static Object

Returns:

the result of invoking the method handle
invoke(MethodHandles.Lookup
unused
lookup, String
unused
name, Class<?>
the desired type of the value to be returned, which must be compatible with the return type of the method handle
type, MethodHandle
the method handle to be invoked
handle, Object...
the arguments to pass to the method handle, as if with MethodHandle#invokeWithArguments. Each argument may be null.
args)

Returns the result of invoking a method handle with the provided arguments.

pack-priv static Object
makeConstant(MethodHandle bootstrapMethod, String name, Class<?> type, Object info, Class<?> callerClass)

public static Object

Returns:

a null value
nullConstant(MethodHandles.Lookup
unused
lookup, String
unused
name, Class<?>
a reference type
type)

Returns a null object reference for the reference type specified by type.

public static Class<?>

Returns:

the Class mirror
primitiveClass(MethodHandles.Lookup
unused
lookup, String
the descriptor (JVMS 4.3) of the desired primitive type
name, Class<?>
the required result type (must be Class.class)
type)

Returns a Class mirror for the primitive type whose type descriptor is specified by name.

public static VarHandle

Returns:

the VarHandle
staticFieldVarHandle(MethodHandles.Lookup
the lookup context describing the class performing the operation (normally stacked by the JVM)
lookup, String
the name of the field
name, Class<VarHandle>
the required result type (must be Class<VarHandle>)
type, Class<?>
the class in which the field is declared
declaringClass, Class<?>
the type of the field
fieldType)

Finds a VarHandle for a static field.

private static <T> Class<T>
validateClassAccess(MethodHandles.Lookup lookup, Class<T> type)

Inherited from java.lang.Object:
cloneequalsfinalizegetClasshashCodenotifynotifyAlltoStringwaitwaitwait

Constructor Detail

ConstantBootstrapsback to summary
private ConstantBootstraps()

Do not call.

Method Detail

arrayVarHandleback to summary
public static VarHandle arrayVarHandle(MethodHandles.Lookup lookup, String name, Class<VarHandle> type, Class<?> arrayClass)

Finds a VarHandle for an array type.

Parameters
lookup:MethodHandles.Lookup

the lookup context describing the class performing the operation (normally stacked by the JVM)

name:String

unused

type:Class<VarHandle>

the required result type (must be Class<VarHandle>)

arrayClass:Class<?>

the type of the array

Returns:VarHandle

the VarHandle

Exceptions
IllegalAccessError:
if the component type of the array is not accessible to the class performing the operation
IllegalArgumentException:
if the type is not VarHandle
enumConstantback to summary
public static <E extends Enum<E>> E enumConstant(MethodHandles.Lookup lookup, String name, Class<E> type)

Returns an enum constant of the type specified by type with the name specified by name.

Parameters
<E>
The enum type for which a constant value is to be returned
lookup:MethodHandles.Lookup

the lookup context describing the class performing the operation (normally stacked by the JVM)

name:String

the name of the constant to return, which must exactly match an enum constant in the specified type.

type:Class<E>

the Class object describing the enum type for which a constant is to be returned

Returns:E

the enum constant of the specified enum type with the specified name

Exceptions
IllegalAccessError:
if the declaring class or the field is not accessible to the class performing the operation
IllegalArgumentException:
if the specified enum type has no constant with the specified name, or the specified class object does not represent an enum type
See Also
Enum#valueOf(Class, String)
explicitCastback to summary
public static Object explicitCast(MethodHandles.Lookup lookup, String name, Class<?> dstType, Object value) throws ClassCastException

Applies a conversion from a source type to a destination type.

Given a destination type dstType and an input value value, one of the following will happen:

  • If dstType is void.class, a ClassCastException is thrown.
  • If dstType is Object.class, value is returned as is.

Otherwise one of the following conversions is applied to value:

  1. If dstType is a reference type, a reference cast is applied to value as if by calling dstType.cast(value).
  2. If dstType is a primitive type, then, if the runtime type of value is a primitive wrapper type (such as Integer), a Java unboxing conversion is applied 5.1.8 followed by a Java casting conversion 5.5 converting either directly to dstType, or, if dstType is boolean, to int, which is then converted to either true or false depending on whether the least-significant-bit is 1 or 0 respectively. If the runtime type of value is not a primitive wrapper type a ClassCastException is thrown.

The result is the same as when using the following code: 

MethodHandle id = MethodHandles.identity(dstType);
MethodType mt = MethodType.methodType(dstType, Object.class);
MethodHandle conv = MethodHandles.explicitCastArguments(id, mt);
return conv.invoke(value);
Parameters
lookup:MethodHandles.Lookup

unused

name:String

unused

dstType:Class<?>

the destination type of the conversion

value:Object

the value to be converted

Returns:Object

the converted value

Exceptions
ClassCastException:
when dstType is void, when a cast per (1) fails, or when dstType is a primitive type and the runtime type of value is not a primitive wrapper type (such as Integer)
Since
15
fieldVarHandleback to summary
public static VarHandle fieldVarHandle(MethodHandles.Lookup lookup, String name, Class<VarHandle> type, Class<?> declaringClass, Class<?> fieldType)

Finds a VarHandle for an instance field.

Parameters
lookup:MethodHandles.Lookup

the lookup context describing the class performing the operation (normally stacked by the JVM)

name:String

the name of the field

type:Class<VarHandle>

the required result type (must be Class<VarHandle>)

declaringClass:Class<?>

the class in which the field is declared

fieldType:Class<?>

the type of the field

Returns:VarHandle

the VarHandle

Exceptions
IllegalAccessError:
if the declaring class or the field is not accessible to the class performing the operation
NoSuchFieldError:
if the specified field does not exist
IllegalArgumentException:
if the type is not VarHandle
getStaticFinalback to summary
public static Object getStaticFinal(MethodHandles.Lookup lookup, String name, Class<?> type, Class<?> declaringClass)

Returns the value of a static final field.

Parameters
lookup:MethodHandles.Lookup

the lookup context describing the class performing the operation (normally stacked by the JVM)

name:String

the name of the field

type:Class<?>

the type of the field

declaringClass:Class<?>

the class in which the field is declared

Returns:Object

the value of the field

Exceptions
IllegalAccessError:
if the declaring class or the field is not accessible to the class performing the operation
NoSuchFieldError:
if the specified field does not exist
IncompatibleClassChangeError:
if the specified field is not final
getStaticFinalback to summary
public static Object getStaticFinal(MethodHandles.Lookup lookup, String name, Class<?> type)

Returns the value of a static final field declared in the class which is the same as the field's type (or, for primitive-valued fields, declared in the wrapper class.) This is a simplified form of getStaticFinal(MethodHandles.Lookup, String, Class, Class) for the case where a class declares distinguished constant instances of itself.

Parameters
lookup:MethodHandles.Lookup

the lookup context describing the class performing the operation (normally stacked by the JVM)

name:String

the name of the field

type:Class<?>

the type of the field

Returns:Object

the value of the field

Exceptions
IllegalAccessError:
if the declaring class or the field is not accessible to the class performing the operation
NoSuchFieldError:
if the specified field does not exist
IncompatibleClassChangeError:
if the specified field is not final
See Also
getStaticFinal(MethodHandles.Lookup, String, Class, Class)
invokeback to summary
public static Object invoke(MethodHandles.Lookup lookup, String name, Class<?> type, MethodHandle handle, Object... args) throws Throwable

Returns the result of invoking a method handle with the provided arguments.

This method behaves as if the method handle to be invoked is the result of adapting the given method handle, via MethodHandle#asType, to adjust the return type to the desired type.

Parameters
lookup:MethodHandles.Lookup

unused

name:String

unused

type:Class<?>

the desired type of the value to be returned, which must be compatible with the return type of the method handle

handle:MethodHandle

the method handle to be invoked

args:Object[]

the arguments to pass to the method handle, as if with MethodHandle#invokeWithArguments. Each argument may be null.

Returns:Object

the result of invoking the method handle

Exceptions
Throwable:
anything thrown by the method handle invocation
WrongMethodTypeException:
if the handle's method type cannot be adjusted to take the given number of arguments, or if the handle's return type cannot be adjusted to the desired type
ClassCastException:
if an argument or the result produced by invoking the handle cannot be converted by reference casting
makeConstantback to summary
pack-priv static Object makeConstant(MethodHandle bootstrapMethod, String name, Class<?> type, Object info, Class<?> callerClass)
nullConstantback to summary
public static Object nullConstant(MethodHandles.Lookup lookup, String name, Class<?> type)

Returns a null object reference for the reference type specified by type.

Parameters
lookup:MethodHandles.Lookup

unused

name:String

unused

type:Class<?>

a reference type

Returns:Object

a null value

Exceptions
IllegalArgumentException:
if type is not a reference type
primitiveClassback to summary
public static Class<?> primitiveClass(MethodHandles.Lookup lookup, String name, Class<?> type)

Returns a Class mirror for the primitive type whose type descriptor is specified by name.

Parameters
lookup:MethodHandles.Lookup

unused

name:String

the descriptor (JVMS 4.3) of the desired primitive type

type:Class<?>

the required result type (must be Class.class)

Returns:Class<?>

the Class mirror

Exceptions
IllegalArgumentException:
if the name is not a descriptor for a primitive type or the type is not Class.class
staticFieldVarHandleback to summary
public static VarHandle staticFieldVarHandle(MethodHandles.Lookup lookup, String name, Class<VarHandle> type, Class<?> declaringClass, Class<?> fieldType)

Finds a VarHandle for a static field.

Parameters
lookup:MethodHandles.Lookup

the lookup context describing the class performing the operation (normally stacked by the JVM)

name:String

the name of the field

type:Class<VarHandle>

the required result type (must be Class<VarHandle>)

declaringClass:Class<?>

the class in which the field is declared

fieldType:Class<?>

the type of the field

Returns:VarHandle

the VarHandle

Exceptions
IllegalAccessError:
if the declaring class or the field is not accessible to the class performing the operation
NoSuchFieldError:
if the specified field does not exist
IllegalArgumentException:
if the type is not VarHandle
validateClassAccessback to summary
private static <T> Class<T> validateClassAccess(MethodHandles.Lookup lookup, Class<T> type)