- All Implemented Interfaces:
Constable
VarHandles are immutable and have no visible state. VarHandles cannot be subclassed by the user.
A VarHandle has:
- a
variable type
T, the type of every variable referenced by this VarHandle; and - a list of
coordinate types
CT1, CT2, ..., CTn
, the types of coordinate expressions that jointly locate a variable referenced by this VarHandle.
Class
objects. The list of coordinate types may be
empty.
Factory methods that produce or lookup
VarHandle instances document the supported variable type and the list
of coordinate types.
Each access mode is associated with one access mode method, a signature polymorphic method named for the access mode. When an access mode method is invoked on a VarHandle instance, the initial arguments to the invocation are coordinate expressions that indicate in precisely which object the variable is to be accessed. Trailing arguments to the invocation represent values of importance to the access mode. For example, the various compare-and-set or compare-and-exchange access modes require two trailing arguments for the variable's expected value and new value.
The arity and types of arguments to the invocation of an access mode
method are not checked statically. Instead, each access mode method
specifies an access mode type
,
represented as an instance of MethodType
, that serves as a kind of
method signature against which the arguments are checked dynamically. An
access mode type gives formal parameter types in terms of the coordinate
types of a VarHandle instance and the types for values of importance to the
access mode. An access mode type also gives a return type, often in terms of
the variable type of a VarHandle instance. When an access mode method is
invoked on a VarHandle instance, the symbolic type descriptor at the
call site, the run time types of arguments to the invocation, and the run
time type of the return value, must match the types
given in the access mode type. A runtime exception will be thrown if the
match fails.
For example, the access mode method compareAndSet(java.lang.Object...)
specifies that if
its receiver is a VarHandle instance with coordinate types
CT1, ..., CTn
and variable type T
, then its access mode type
is (CT1 c1, ..., CTn cn, T expectedValue, T newValue)boolean
.
Suppose that a VarHandle instance can access array elements, and that its
coordinate types are String[]
and int
while its variable type
is String
. The access mode type for compareAndSet
on this
VarHandle instance would be
(String[] c1, int c2, String expectedValue, String newValue)boolean
.
Such a VarHandle instance may be produced by the
array factory method
and
access array elements as follows:
String[] sa = ...
VarHandle avh = MethodHandles.arrayElementVarHandle(String[].class);
boolean r = avh.compareAndSet(sa, 10, "expected", "new");
Access modes control atomicity and consistency properties.
Plain read (get
) and write (set
)
accesses are guaranteed to be bitwise atomic only for references
and for primitive values of at most 32 bits, and impose no observable
ordering constraints with respect to threads other than the
executing thread. Opaque operations are bitwise atomic and
coherently ordered with respect to accesses to the same variable.
In addition to obeying Opaque properties, Acquire mode
reads and their subsequent accesses are ordered after matching
Release mode writes and their previous accesses. In
addition to obeying Acquire and Release properties, all
Volatile operations are totally ordered with respect to
each other.
Access modes are grouped into the following categories:
- read access modes that get the value of a variable under specified
memory ordering effects.
The set of corresponding access mode methods belonging to this group
consists of the methods
get
,getVolatile
,getAcquire
,getOpaque
. - write access modes that set the value of a variable under specified
memory ordering effects.
The set of corresponding access mode methods belonging to this group
consists of the methods
set
,setVolatile
,setRelease
,setOpaque
. - atomic update access modes that, for example, atomically compare and set
the value of a variable under specified memory ordering effects.
The set of corresponding access mode methods belonging to this group
consists of the methods
compareAndSet
,weakCompareAndSetPlain
,weakCompareAndSet
,weakCompareAndSetAcquire
,weakCompareAndSetRelease
,compareAndExchangeAcquire
,compareAndExchange
,compareAndExchangeRelease
,getAndSet
,getAndSetAcquire
,getAndSetRelease
. - numeric atomic update access modes that, for example, atomically get and
set with addition the value of a variable under specified memory ordering
effects.
The set of corresponding access mode methods belonging to this group
consists of the methods
getAndAdd
,getAndAddAcquire
,getAndAddRelease
, - bitwise atomic update access modes that, for example, atomically get and
bitwise OR the value of a variable under specified memory ordering
effects.
The set of corresponding access mode methods belonging to this group
consists of the methods
getAndBitwiseOr
,getAndBitwiseOrAcquire
,getAndBitwiseOrRelease
,getAndBitwiseAnd
,getAndBitwiseAndAcquire
,getAndBitwiseAndRelease
,getAndBitwiseXor
,getAndBitwiseXorAcquire
,getAndBitwiseXorRelease
.
Factory methods that produce or lookup
VarHandle instances document the set of access modes that are
supported, which may also include documenting restrictions based on the
variable type and whether a variable is read-only. If an access mode is not
supported then the corresponding access mode method will on invocation throw
an UnsupportedOperationException
. Factory methods should document
any additional undeclared exceptions that may be thrown by access mode
methods.
The get
access mode is supported for all
VarHandle instances and the corresponding method never throws
UnsupportedOperationException
.
If a VarHandle references a read-only variable (for example a final
field) then write, atomic update, numeric atomic update, and bitwise atomic
update access modes are not supported and corresponding methods throw
UnsupportedOperationException
.
Read/write access modes (if supported), with the exception of
get
and set
, provide atomic access for
reference types and all primitive types.
Unless stated otherwise in the documentation of a factory method, the access
modes get
and set
(if supported) provide atomic access for
reference types and all primitives types, with the exception of long
and double
on 32-bit platforms.
Access modes will override any memory ordering effects specified at
the declaration site of a variable. For example, a VarHandle accessing
a field using the get
access mode will access the field as
specified by its access mode even if that field is declared
volatile
. When mixed access is performed extreme care should be
taken since the Java Memory Model may permit surprising results.
In addition to supporting access to variables under various access modes,
a set of static methods, referred to as memory fence methods, is also
provided for fine-grained control of memory ordering.
The Java Language Specification permits other threads to observe operations
as if they were executed in orders different than are apparent in program
source code, subject to constraints arising, for example, from the use of
locks, volatile
fields or VarHandles. The static methods,
fullFence
, acquireFence
,
releaseFence
, loadLoadFence
and
storeStoreFence
, can also be used to impose
constraints. Their specifications, as is the case for certain access modes,
are phrased in terms of the lack of "reorderings" -- observable ordering
effects that might otherwise occur if the fence was not present. More
precise phrasing of the specification of access mode methods and memory fence
methods may accompany future updates of the Java Language Specification.
Compiling invocation of access mode methods
A Java method call expression naming an access mode method can invoke a VarHandle from Java source code. From the viewpoint of source code, these methods can take any arguments and their polymorphic result (if expressed) can be cast to any return type. Formally this is accomplished by giving the access mode methods variable arityObject
arguments and
Object
return types (if the return type is polymorphic), but they
have an additional quality called signature polymorphism which
connects this freedom of invocation directly to the JVM execution stack.
As is usual with virtual methods, source-level calls to access mode methods
compile to an invokevirtual
instruction. More unusually, the
compiler must record the actual argument types, and may not perform method
invocation conversions on the arguments. Instead, it must generate
instructions to push them on the stack according to their own unconverted
types. The VarHandle object itself will be pushed on the stack before the
arguments. The compiler then generates an invokevirtual
instruction
that invokes the access mode method with a symbolic type descriptor which
describes the argument and return types.
To issue a complete symbolic type descriptor, the compiler must also
determine the return type (if polymorphic). This is based on a cast on the
method invocation expression, if there is one, or else Object
if the
invocation is an expression, or else void
if the invocation is a
statement. The cast may be to a primitive type (but not void
).
As a corner case, an uncasted null
argument is given a symbolic type
descriptor of java.lang.Void
. The ambiguity with the type
Void
is harmless, since there are no references of type Void
except the null reference.
Performing invocation of access mode methods
The first time aninvokevirtual
instruction is executed it is linked
by symbolically resolving the names in the instruction and verifying that
the method call is statically legal. This also holds for calls to access mode
methods. In this case, the symbolic type descriptor emitted by the compiler
is checked for correct syntax, and names it contains are resolved. Thus, an
invokevirtual
instruction which invokes an access mode method will
always link, as long as the symbolic type descriptor is syntactically
well-formed and the types exist.
When the invokevirtual
is executed after linking, the receiving
VarHandle's access mode type is first checked by the JVM to ensure that it
matches the symbolic type descriptor. If the type
match fails, it means that the access mode method which the caller is
invoking is not present on the individual VarHandle being invoked.
Invocation of an access mode method behaves, by default, as if an invocation of
MethodHandle.invoke(java.lang.Object...)
, where the receiving method handle accepts the
VarHandle instance as the leading argument. More specifically, the
following, where {access-mode}
corresponds to the access mode method
name:
VarHandle vh = ..
R r = (R) vh.{access-mode}(p1, p2, ..., pN);
behaves as if:
VarHandle vh = ..
VarHandle.AccessMode am = VarHandle.AccessMode.valueFromMethodName("{access-mode}");
MethodHandle mh = MethodHandles.varHandleExactInvoker(
am,
vh.accessModeType(am));
R r = (R) mh.invoke(vh, p1, p2, ..., pN)
(modulo access mode methods do not declare throwing of Throwable
).
This is equivalent to:
MethodHandle mh = MethodHandles.lookup().findVirtual(
VarHandle.class,
"{access-mode}",
MethodType.methodType(R, p1, p2, ..., pN));
R r = (R) mh.invokeExact(vh, p1, p2, ..., pN)
where the desired method type is the symbolic type descriptor and a
MethodHandle.invokeExact(java.lang.Object...)
is performed, since before invocation of the
target, the handle will apply reference casts as necessary and box, unbox, or
widen primitive values, as if by asType
(see also
MethodHandles.varHandleInvoker(java.lang.invoke.VarHandle.AccessMode, java.lang.invoke.MethodType)
).
More concisely, such behavior is equivalent to:
VarHandle vh = ..
VarHandle.AccessMode am = VarHandle.AccessMode.valueFromMethodName("{access-mode}");
MethodHandle mh = vh.toMethodHandle(am);
R r = (R) mh.invoke(p1, p2, ..., pN)
Where, in this case, the method handle is bound to the VarHandle instance.
A VarHandle's invocation behavior can be adjusted (see withInvokeExactBehavior()
) such that invocation of
an access mode method behaves as if invocation of MethodHandle.invokeExact(java.lang.Object...)
,
where the receiving method handle accepts the VarHandle instance as the leading argument.
More specifically, the following, where {access-mode}
corresponds to the access mode method
name:
VarHandle vh = ..
R r = (R) vh.{access-mode}(p1, p2, ..., pN);
behaves as if:
VarHandle vh = ..
VarHandle.AccessMode am = VarHandle.AccessMode.valueFromMethodName("{access-mode}");
MethodHandle mh = MethodHandles.varHandleExactInvoker(
am,
vh.accessModeType(am));
R r = (R) mh.invokeExact(vh, p1, p2, ..., pN)
(modulo access mode methods do not declare throwing of Throwable
).
More concisely, such behavior is equivalent to:
VarHandle vh = ..
VarHandle.AccessMode am = VarHandle.AccessMode.valueFromMethodName("{access-mode}");
MethodHandle mh = vh.toMethodHandle(am);
R r = (R) mh.invokeExact(p1, p2, ..., pN)
Where, in this case, the method handle is bound to the VarHandle instance.
Invocation checking
In typical programs, VarHandle access mode type matching will usually succeed. But if a match fails, the JVM will throw aWrongMethodTypeException
.
Thus, an access mode type mismatch which might show up as a linkage error
in a statically typed program can show up as a dynamic
WrongMethodTypeException
in a program which uses VarHandles.
Because access mode types contain "live" Class
objects, method type
matching takes into account both type names and class loaders.
Thus, even if a VarHandle VH
is created in one class loader
L1
and used in another L2
, VarHandle access mode method
calls are type-safe, because the caller's symbolic type descriptor, as
resolved in L2
, is matched against the original callee method's
symbolic type descriptor, as resolved in L1
. The resolution in
L1
happens when VH
is created and its access mode types are
assigned, while the resolution in L2
happens when the
invokevirtual
instruction is linked.
Apart from type descriptor checks, a VarHandles's capability to access its variables is unrestricted. If a VarHandle is formed on a non-public variable by a class that has access to that variable, the resulting VarHandle can be used in any place by any caller who receives a reference to it.
Unlike with the Core Reflection API, where access is checked every time a reflective method is invoked, VarHandle access checking is performed when the VarHandle is created. Thus, VarHandles to non-public variables, or to variables in non-public classes, should generally be kept secret. They should not be passed to untrusted code unless their use from the untrusted code would be harmless.
VarHandle creation
Java code can create a VarHandle that directly accesses any field that is accessible to that code. This is done via a reflective, capability-based API calledMethodHandles.Lookup
.
For example, a VarHandle for a non-static field can be obtained
from Lookup.findVarHandle
.
There is also a conversion method from Core Reflection API objects,
Lookup.unreflectVarHandle
.
Access to protected field members is restricted to receivers only of the accessing class, or one of its subclasses, and the accessing class must in turn be a subclass (or package sibling) of the protected member's defining class. If a VarHandle refers to a protected non-static field of a declaring class outside the current package, the receiver argument will be narrowed to the type of the accessing class.
Interoperation between VarHandles and the Core Reflection API
Using factory methods in theLookup
API, any field represented by a Core Reflection API object
can be converted to a behaviorally equivalent VarHandle.
For example, a reflective Field
can
be converted to a VarHandle using
Lookup.unreflectVarHandle
.
The resulting VarHandles generally provide more direct and efficient
access to the underlying fields.
As a special case, when the Core Reflection API is used to view the
signature polymorphic access mode methods in this class, they appear as
ordinary non-polymorphic methods. Their reflective appearance, as viewed by
Class.getDeclaredMethod
,
is unaffected by their special status in this API.
For example, Method.getModifiers
will report exactly those modifier bits required for any similarly
declared method, including in this case native
and varargs
bits.
As with any reflected method, these methods (when reflected) may be invoked
directly via java.lang.reflect.Method.invoke
,
via JNI, or indirectly via
Lookup.unreflect
.
However, such reflective calls do not result in access mode method
invocations. Such a call, if passed the required argument (a single one, of
type Object[]
), will ignore the argument and will throw an
UnsupportedOperationException
.
Since invokevirtual
instructions can natively invoke VarHandle
access mode methods under any symbolic type descriptor, this reflective view
conflicts with the normal presentation of these methods via bytecodes.
Thus, these native methods, when reflectively viewed by
Class.getDeclaredMethod
, may be regarded as placeholders only.
In order to obtain an invoker method for a particular access mode type,
use MethodHandles.varHandleExactInvoker(java.lang.invoke.VarHandle.AccessMode, java.lang.invoke.MethodType)
or
MethodHandles.varHandleInvoker(java.lang.invoke.VarHandle.AccessMode, java.lang.invoke.MethodType)
. The
Lookup.findVirtual
API is also able to return a method handle to call an access mode method for
any specified access mode type and is equivalent in behavior to
MethodHandles.varHandleInvoker(java.lang.invoke.VarHandle.AccessMode, java.lang.invoke.MethodType)
.
Interoperation between VarHandles and Java generics
A VarHandle can be obtained for a variable, such as a field, which is declared with Java generic types. As with the Core Reflection API, the VarHandle's variable type will be constructed from the erasure of the source-level type. When a VarHandle access mode method is invoked, the types of its arguments or the return value cast type may be generic types or type instances. If this occurs, the compiler will replace those types by their erasures when it constructs the symbolic type descriptor for theinvokevirtual
instruction.- Since:
- 9
- See Also:
-
Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic enum
The set of access modes that specify how a variable, referenced by a VarHandle, is accessed.static final class
A nominal descriptor for aVarHandle
constant. -
Method Summary
Modifier and TypeMethodDescriptionfinal MethodType
accessModeType
(VarHandle.AccessMode accessMode) Obtains the access mode type for this VarHandle and a given access mode.static void
Ensures that loads before the fence will not be reordered with loads and stores after the fence.final Object
compareAndExchange
(Object... args) Atomically sets the value of a variable to thenewValue
with the memory semantics ofsetVolatile(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.final Object
compareAndExchangeAcquire
(Object... args) Atomically sets the value of a variable to thenewValue
with the memory semantics ofset(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.final Object
compareAndExchangeRelease
(Object... args) Atomically sets the value of a variable to thenewValue
with the memory semantics ofsetRelease(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofget(java.lang.Object...)
.final boolean
compareAndSet
(Object... args) Atomically sets the value of a variable to thenewValue
with the memory semantics ofsetVolatile(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.Returns the coordinate types for this VarHandle.Return a nominal descriptor for this instance, if one can be constructed, or an emptyOptional
if one cannot be.static void
Ensures that loads and stores before the fence will not be reordered with loads and stores after the fence.final Object
Returns the value of a variable, with memory semantics of reading as if the variable was declared non-volatile
.final Object
getAcquire
(Object... args) Returns the value of a variable, and ensures that subsequent loads and stores are not reordered before this access.final Object
Atomically adds thevalue
to the current value of a variable with the memory semantics ofsetVolatile(java.lang.Object...)
, and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.final Object
getAndAddAcquire
(Object... args) Atomically adds thevalue
to the current value of a variable with the memory semantics ofset(java.lang.Object...)
, and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.final Object
getAndAddRelease
(Object... args) Atomically adds thevalue
to the current value of a variable with the memory semantics ofsetRelease(java.lang.Object...)
, and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...)
.final Object
getAndBitwiseAnd
(Object... args) Atomically sets the value of a variable to the result of bitwise AND between the variable's current value and themask
with the memory semantics ofsetVolatile(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.final Object
getAndBitwiseAndAcquire
(Object... args) Atomically sets the value of a variable to the result of bitwise AND between the variable's current value and themask
with the memory semantics ofset(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.final Object
getAndBitwiseAndRelease
(Object... args) Atomically sets the value of a variable to the result of bitwise AND between the variable's current value and themask
with the memory semantics ofsetRelease(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...)
.final Object
getAndBitwiseOr
(Object... args) Atomically sets the value of a variable to the result of bitwise OR between the variable's current value and themask
with the memory semantics ofsetVolatile(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.final Object
getAndBitwiseOrAcquire
(Object... args) Atomically sets the value of a variable to the result of bitwise OR between the variable's current value and themask
with the memory semantics ofset(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.final Object
getAndBitwiseOrRelease
(Object... args) Atomically sets the value of a variable to the result of bitwise OR between the variable's current value and themask
with the memory semantics ofsetRelease(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...)
.final Object
getAndBitwiseXor
(Object... args) Atomically sets the value of a variable to the result of bitwise XOR between the variable's current value and themask
with the memory semantics ofsetVolatile(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.final Object
getAndBitwiseXorAcquire
(Object... args) Atomically sets the value of a variable to the result of bitwise XOR between the variable's current value and themask
with the memory semantics ofset(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.final Object
getAndBitwiseXorRelease
(Object... args) Atomically sets the value of a variable to the result of bitwise XOR between the variable's current value and themask
with the memory semantics ofsetRelease(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...)
.final Object
Atomically sets the value of a variable to thenewValue
with the memory semantics ofsetVolatile(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.final Object
getAndSetAcquire
(Object... args) Atomically sets the value of a variable to thenewValue
with the memory semantics ofset(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.final Object
getAndSetRelease
(Object... args) Atomically sets the value of a variable to thenewValue
with the memory semantics ofsetRelease(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...)
.final Object
Returns the value of a variable, accessed in program order, but with no assurance of memory ordering effects with respect to other threads.final Object
getVolatile
(Object... args) Returns the value of a variable, with memory semantics of reading as if the variable was declaredvolatile
.boolean
Returnstrue
if this VarHandle has invoke-exact behavior.boolean
isAccessModeSupported
(VarHandle.AccessMode accessMode) Returnstrue
if the given access mode is supported, otherwisefalse
.static void
Ensures that loads before the fence will not be reordered with loads after the fence.static void
Ensures that loads and stores before the fence will not be reordered with stores after the fence.final void
Sets the value of a variable to thenewValue
, with memory semantics of setting as if the variable was declared non-volatile
and non-final
.final void
Sets the value of a variable to thenewValue
, in program order, but with no assurance of memory ordering effects with respect to other threads.final void
setRelease
(Object... args) Sets the value of a variable to thenewValue
, and ensures that prior loads and stores are not reordered after this access.final void
setVolatile
(Object... args) Sets the value of a variable to thenewValue
, with memory semantics of setting as if the variable was declaredvolatile
.static void
Ensures that stores before the fence will not be reordered with stores after the fence.toMethodHandle
(VarHandle.AccessMode accessMode) Obtains a method handle bound to this VarHandle and the given access mode.final String
toString()
Returns a compact textual description of this VarHandle, including the type of variable described, and a description of its coordinates.Class
<?> varType()
Returns the variable type of variables referenced by this VarHandle.final boolean
weakCompareAndSet
(Object... args) Possibly atomically sets the value of a variable to thenewValue
with the memory semantics ofsetVolatile(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.final boolean
weakCompareAndSetAcquire
(Object... args) Possibly atomically sets the value of a variable to thenewValue
with the semantics ofset(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.final boolean
weakCompareAndSetPlain
(Object... args) Possibly atomically sets the value of a variable to thenewValue
with the semantics ofset(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofget(java.lang.Object...)
.final boolean
weakCompareAndSetRelease
(Object... args) Possibly atomically sets the value of a variable to thenewValue
with the semantics ofsetRelease(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofget(java.lang.Object...)
.abstract VarHandle
Returns a VarHandle, with access to the same variable(s) as this VarHandle, but whose invocation behavior of access mode methods is adjusted to invoke behavior.abstract VarHandle
Returns a VarHandle, with access to the same variable(s) as this VarHandle, but whose invocation behavior of access mode methods is adjusted to invoke-exact behavior.
-
Method Details
-
hasInvokeExactBehavior
public boolean hasInvokeExactBehavior()Returnstrue
if this VarHandle has invoke-exact behavior.- Returns:
true
if this VarHandle has invoke-exact behavior.- Since:
- 16
- See Also:
-
get
Returns the value of a variable, with memory semantics of reading as if the variable was declared non-volatile
. Commonly referred to as plain read access.The method signature is of the form
(CT1 ct1, ..., CTn ctn)T
.The symbolic type descriptor at the call site of
get
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET)
on this VarHandle.This access mode is supported by all VarHandle instances and never throws
UnsupportedOperationException
.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the value of the
variable
, statically represented using
Object
. - Throws:
WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
-
set
Sets the value of a variable to thenewValue
, with memory semantics of setting as if the variable was declared non-volatile
and non-final
. Commonly referred to as plain write access.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T newValue)void
The symbolic type descriptor at the call site of
set
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.SET)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue)
, statically represented using varargs.- Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
-
getVolatile
Returns the value of a variable, with memory semantics of reading as if the variable was declaredvolatile
.The method signature is of the form
(CT1 ct1, ..., CTn ctn)T
.The symbolic type descriptor at the call site of
getVolatile
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_VOLATILE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the value of the
variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
-
setVolatile
Sets the value of a variable to thenewValue
, with memory semantics of setting as if the variable was declaredvolatile
.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T newValue)void
.The symbolic type descriptor at the call site of
setVolatile
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.SET_VOLATILE)
on this VarHandle.- API Note:
- Ignoring the many semantic differences from C and C++, this method has
memory ordering effects compatible with
memory_order_seq_cst
. - Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue)
, statically represented using varargs.- Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
-
getOpaque
Returns the value of a variable, accessed in program order, but with no assurance of memory ordering effects with respect to other threads.The method signature is of the form
(CT1 ct1, ..., CTn ctn)T
.The symbolic type descriptor at the call site of
getOpaque
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_OPAQUE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the value of the
variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
-
setOpaque
Sets the value of a variable to thenewValue
, in program order, but with no assurance of memory ordering effects with respect to other threads.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T newValue)void
.The symbolic type descriptor at the call site of
setOpaque
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.SET_OPAQUE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue)
, statically represented using varargs.- Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
-
getAcquire
Returns the value of a variable, and ensures that subsequent loads and stores are not reordered before this access.The method signature is of the form
(CT1 ct1, ..., CTn ctn)T
.The symbolic type descriptor at the call site of
getAcquire
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_ACQUIRE)
on this VarHandle.- API Note:
- Ignoring the many semantic differences from C and C++, this method has
memory ordering effects compatible with
memory_order_acquire
ordering. - Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the value of the
variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
-
setRelease
Sets the value of a variable to thenewValue
, and ensures that prior loads and stores are not reordered after this access.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T newValue)void
.The symbolic type descriptor at the call site of
setRelease
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.SET_RELEASE)
on this VarHandle.- API Note:
- Ignoring the many semantic differences from C and C++, this method has
memory ordering effects compatible with
memory_order_release
ordering. - Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue)
, statically represented using varargs.- Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.
-
compareAndSet
Atomically sets the value of a variable to thenewValue
with the memory semantics ofsetVolatile(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean
.The symbolic type descriptor at the call site of
compareAndSet
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.COMPARE_AND_SET)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)
, statically represented using varargs.- Returns:
true
if successful, otherwisefalse
if the witness value was not the same as theexpectedValue
.- Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
compareAndExchange
Atomically sets the value of a variable to thenewValue
with the memory semantics ofsetVolatile(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)T
.The symbolic type descriptor at the call site of
compareAndExchange
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.COMPARE_AND_EXCHANGE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the witness value, which
will be the same as the
expectedValue
if successful , statically represented usingObject
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type is not compatible with the caller's symbolic type descriptor.ClassCastException
- if the access mode type is compatible with the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
compareAndExchangeAcquire
Atomically sets the value of a variable to thenewValue
with the memory semantics ofset(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)T
.The symbolic type descriptor at the call site of
compareAndExchangeAcquire
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.COMPARE_AND_EXCHANGE_ACQUIRE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the witness value, which
will be the same as the
expectedValue
if successful , statically represented usingObject
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
compareAndExchangeRelease
Atomically sets the value of a variable to thenewValue
with the memory semantics ofsetRelease(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofget(java.lang.Object...)
.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)T
.The symbolic type descriptor at the call site of
compareAndExchangeRelease
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.COMPARE_AND_EXCHANGE_RELEASE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the witness value, which
will be the same as the
expectedValue
if successful , statically represented usingObject
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
weakCompareAndSetPlain
Possibly atomically sets the value of a variable to thenewValue
with the semantics ofset(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofget(java.lang.Object...)
.This operation may fail spuriously (typically, due to memory contention) even if the witness value does match the expected value.
The method signature is of the form
(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean
.The symbolic type descriptor at the call site of
weakCompareAndSetPlain
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET_PLAIN)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)
, statically represented using varargs.- Returns:
true
if successful, otherwisefalse
if the witness value was not the same as theexpectedValue
or if this operation spuriously failed.- Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
weakCompareAndSet
Possibly atomically sets the value of a variable to thenewValue
with the memory semantics ofsetVolatile(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.This operation may fail spuriously (typically, due to memory contention) even if the witness value does match the expected value.
The method signature is of the form
(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean
.The symbolic type descriptor at the call site of
weakCompareAndSet
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)
, statically represented using varargs.- Returns:
true
if successful, otherwisefalse
if the witness value was not the same as theexpectedValue
or if this operation spuriously failed.- Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
weakCompareAndSetAcquire
Possibly atomically sets the value of a variable to thenewValue
with the semantics ofset(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.This operation may fail spuriously (typically, due to memory contention) even if the witness value does match the expected value.
The method signature is of the form
(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean
.The symbolic type descriptor at the call site of
weakCompareAndSetAcquire
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET_ACQUIRE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)
, statically represented using varargs.- Returns:
true
if successful, otherwisefalse
if the witness value was not the same as theexpectedValue
or if this operation spuriously failed.- Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
weakCompareAndSetRelease
Possibly atomically sets the value of a variable to thenewValue
with the semantics ofsetRelease(java.lang.Object...)
if the variable's current value, referred to as the witness value,==
theexpectedValue
, as accessed with the memory semantics ofget(java.lang.Object...)
.This operation may fail spuriously (typically, due to memory contention) even if the witness value does match the expected value.
The method signature is of the form
(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean
.The symbolic type descriptor at the call site of
weakCompareAndSetRelease
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET_RELEASE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)
, statically represented using varargs.- Returns:
true
if successful, otherwisefalse
if the witness value was not the same as theexpectedValue
or if this operation spuriously failed.- Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndSet
Atomically sets the value of a variable to thenewValue
with the memory semantics ofsetVolatile(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T newValue)T
.The symbolic type descriptor at the call site of
getAndSet
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_SET)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndSetAcquire
Atomically sets the value of a variable to thenewValue
with the memory semantics ofset(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T newValue)T
.The symbolic type descriptor at the call site of
getAndSetAcquire
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_SET_ACQUIRE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndSetRelease
Atomically sets the value of a variable to thenewValue
with the memory semantics ofsetRelease(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...)
.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T newValue)T
.The symbolic type descriptor at the call site of
getAndSetRelease
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_SET_RELEASE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T newValue)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndAdd
Atomically adds thevalue
to the current value of a variable with the memory semantics ofsetVolatile(java.lang.Object...)
, and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T value)T
.The symbolic type descriptor at the call site of
getAndAdd
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_ADD)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T value)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndAddAcquire
Atomically adds thevalue
to the current value of a variable with the memory semantics ofset(java.lang.Object...)
, and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T value)T
.The symbolic type descriptor at the call site of
getAndAddAcquire
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_ADD_ACQUIRE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T value)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndAddRelease
Atomically adds thevalue
to the current value of a variable with the memory semantics ofsetRelease(java.lang.Object...)
, and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...)
.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T value)T
.The symbolic type descriptor at the call site of
getAndAddRelease
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_ADD_RELEASE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T value)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndBitwiseOr
Atomically sets the value of a variable to the result of bitwise OR between the variable's current value and themask
with the memory semantics ofsetVolatile(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.If the variable type is the non-integral
boolean
type then a logical OR is performed instead of a bitwise OR.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T mask)T
.The symbolic type descriptor at the call site of
getAndBitwiseOr
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_OR)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndBitwiseOrAcquire
Atomically sets the value of a variable to the result of bitwise OR between the variable's current value and themask
with the memory semantics ofset(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.If the variable type is the non-integral
boolean
type then a logical OR is performed instead of a bitwise OR.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T mask)T
.The symbolic type descriptor at the call site of
getAndBitwiseOrAcquire
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_OR_ACQUIRE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndBitwiseOrRelease
Atomically sets the value of a variable to the result of bitwise OR between the variable's current value and themask
with the memory semantics ofsetRelease(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...)
.If the variable type is the non-integral
boolean
type then a logical OR is performed instead of a bitwise OR.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T mask)T
.The symbolic type descriptor at the call site of
getAndBitwiseOrRelease
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_OR_RELEASE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndBitwiseAnd
Atomically sets the value of a variable to the result of bitwise AND between the variable's current value and themask
with the memory semantics ofsetVolatile(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.If the variable type is the non-integral
boolean
type then a logical AND is performed instead of a bitwise AND.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T mask)T
.The symbolic type descriptor at the call site of
getAndBitwiseAnd
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_AND)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndBitwiseAndAcquire
Atomically sets the value of a variable to the result of bitwise AND between the variable's current value and themask
with the memory semantics ofset(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.If the variable type is the non-integral
boolean
type then a logical AND is performed instead of a bitwise AND.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T mask)T
.The symbolic type descriptor at the call site of
getAndBitwiseAndAcquire
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_AND_ACQUIRE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndBitwiseAndRelease
Atomically sets the value of a variable to the result of bitwise AND between the variable's current value and themask
with the memory semantics ofsetRelease(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...)
.If the variable type is the non-integral
boolean
type then a logical AND is performed instead of a bitwise AND.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T mask)T
.The symbolic type descriptor at the call site of
getAndBitwiseAndRelease
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_AND_RELEASE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndBitwiseXor
Atomically sets the value of a variable to the result of bitwise XOR between the variable's current value and themask
with the memory semantics ofsetVolatile(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetVolatile(java.lang.Object...)
.If the variable type is the non-integral
boolean
type then a logical XOR is performed instead of a bitwise XOR.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T mask)T
.The symbolic type descriptor at the call site of
getAndBitwiseXor
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_XOR)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndBitwiseXorAcquire
Atomically sets the value of a variable to the result of bitwise XOR between the variable's current value and themask
with the memory semantics ofset(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofgetAcquire(java.lang.Object...)
.If the variable type is the non-integral
boolean
type then a logical XOR is performed instead of a bitwise XOR.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T mask)T
.The symbolic type descriptor at the call site of
getAndBitwiseXorAcquire
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_XOR_ACQUIRE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
getAndBitwiseXorRelease
Atomically sets the value of a variable to the result of bitwise XOR between the variable's current value and themask
with the memory semantics ofsetRelease(java.lang.Object...)
and returns the variable's previous value, as accessed with the memory semantics ofget(java.lang.Object...)
.If the variable type is the non-integral
boolean
type then a logical XOR is performed instead of a bitwise XOR.The method signature is of the form
(CT1 ct1, ..., CTn ctn, T mask)T
.The symbolic type descriptor at the call site of
getAndBitwiseXorRelease
must match the access mode type that is the result of callingaccessModeType(VarHandle.AccessMode.GET_AND_BITWISE_XOR_RELEASE)
on this VarHandle.- Parameters:
args
- the signature-polymorphic parameter list of the form(CT1 ct1, ..., CTn ctn, T mask)
, statically represented using varargs.- Returns:
- the signature-polymorphic result that is the previous value of
the variable
, statically represented using
Object
. - Throws:
UnsupportedOperationException
- if the access mode is unsupported for this VarHandle.WrongMethodTypeException
- if the access mode type does not match the caller's symbolic type descriptor.ClassCastException
- if the access mode type matches the caller's symbolic type descriptor, but a reference cast fails.- See Also:
-
withInvokeExactBehavior
Returns a VarHandle, with access to the same variable(s) as this VarHandle, but whose invocation behavior of access mode methods is adjusted to invoke-exact behavior.If this VarHandle already has invoke-exact behavior this VarHandle is returned.
Invoking
hasInvokeExactBehavior()
on the returned var handle is guaranteed to returntrue
.- API Note:
- Invoke-exact behavior guarantees that upon invocation of an access mode method
the types and arity of the arguments must match the
access mode type
, otherwise aWrongMethodTypeException
is thrown. - Returns:
- a VarHandle with invoke-exact behavior
- Since:
- 16
- See Also:
-
withInvokeBehavior
Returns a VarHandle, with access to the same variable(s) as this VarHandle, but whose invocation behavior of access mode methods is adjusted to invoke behavior.If this VarHandle already has invoke behavior this VarHandle is returned.
Invoking
hasInvokeExactBehavior()
on the returned var handle is guaranteed to returnfalse
.- Returns:
- a VarHandle with invoke behavior
- Since:
- 16
- See Also:
-
toString
-
varType
Returns the variable type of variables referenced by this VarHandle.- Returns:
- the variable type of variables referenced by this VarHandle
-
coordinateTypes
-
accessModeType
Obtains the access mode type for this VarHandle and a given access mode.The access mode type's parameter types will consist of a prefix that is the coordinate types of this VarHandle followed by further types as defined by the access mode method. The access mode type's return type is defined by the return type of the access mode method.
- Parameters:
accessMode
- the access mode, corresponding to the signature-polymorphic method of the same name- Returns:
- the access mode type for the given access mode
-
isAccessModeSupported
Returnstrue
if the given access mode is supported, otherwisefalse
.The return of a
false
value for a given access mode indicates that anUnsupportedOperationException
is thrown on invocation of the corresponding access mode method.- Parameters:
accessMode
- the access mode, corresponding to the signature-polymorphic method of the same name- Returns:
true
if the given access mode is supported, otherwisefalse
.
-
toMethodHandle
Obtains a method handle bound to this VarHandle and the given access mode.- API Note:
- This method, for a VarHandle
vh
and access mode{access-mode}
, returns a method handle that is equivalent to method handlebmh
in the following code (though it may be more efficient):MethodHandle mh = MethodHandles.varHandleExactInvoker( vh.accessModeType(VarHandle.AccessMode.{access-mode})); MethodHandle bmh = mh.bindTo(vh);
- Parameters:
accessMode
- the access mode, corresponding to the signature-polymorphic method of the same name- Returns:
- a method handle bound to this VarHandle and the given access mode
-
describeConstable
Return a nominal descriptor for this instance, if one can be constructed, or an emptyOptional
if one cannot be.- Specified by:
describeConstable
in interfaceConstable
- Returns:
- An
Optional
containing the resulting nominal descriptor, or an emptyOptional
if one cannot be constructed. - Since:
- 12
-
fullFence
public static void fullFence()Ensures that loads and stores before the fence will not be reordered with loads and stores after the fence.- API Note:
- Ignoring the many semantic differences from C and C++, this
method has memory ordering effects compatible with
atomic_thread_fence(memory_order_seq_cst)
-
acquireFence
public static void acquireFence()Ensures that loads before the fence will not be reordered with loads and stores after the fence.- API Note:
- Ignoring the many semantic differences from C and C++, this
method has memory ordering effects compatible with
atomic_thread_fence(memory_order_acquire)
-
releaseFence
public static void releaseFence()Ensures that loads and stores before the fence will not be reordered with stores after the fence.- API Note:
- Ignoring the many semantic differences from C and C++, this
method has memory ordering effects compatible with
atomic_thread_fence(memory_order_release)
-
loadLoadFence
public static void loadLoadFence()Ensures that loads before the fence will not be reordered with loads after the fence. -
storeStoreFence
public static void storeStoreFence()Ensures that stores before the fence will not be reordered with stores after the fence.
-