Class VolatileCallSite

java.lang.Object

java.lang.invoke.CallSite

java.lang.invoke.VolatileCallSite

public non-sealed class VolatileCallSite extends CallSite

A VolatileCallSite is a CallSite whose target acts like a volatile variable. An invokedynamic instruction linked to a VolatileCallSite sees updates to its call site target immediately, even if the update occurs in another thread. There may be a performance penalty for such tight coupling between threads.

Unlike MutableCallSite, there is no syncAll operation on volatile call sites, since every write to a volatile variable is implicitly synchronized with reader threads.

In other respects, a VolatileCallSite is interchangeable with MutableCallSite.

Since:

1.7

See Also:

Constructor Summary

Constructor	Description
`VolatileCallSite(MethodHandle target)`	Creates a call site with a volatile binding to its target.
`VolatileCallSite(MethodType type)`	Creates a call site with a volatile binding to its target.

Method Summary

Modifier and Type	Method	Description
`final MethodHandle`	`dynamicInvoker()`	Produces a method handle equivalent to an invokedynamic instruction which has been linked to this call site.
`final MethodHandle`	`getTarget()`	Returns the target method of the call site, which behaves like a `volatile` field of the `VolatileCallSite`.
`void`	`setTarget(MethodHandle newTarget)`	Updates the target method of this call site, as a volatile variable.

Methods declared in class CallSite

type

Modifier and Type	Method	Description
`MethodType`	`type()`	Returns the type of this call site's target.

Methods declared in class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Modifier and Type	Method	Description
`protected Object`	`clone()`	Creates and returns a copy of this object.
`boolean`	`equals(Object obj)`	Indicates whether some other object is "equal to" this one.
`protected void`	`finalize()`	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
`final Class<?>`	`getClass()`	Returns the runtime class of this `Object`.
`int`	`hashCode()`	Returns a hash code value for this object.
`final void`	`notify()`	Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()`	Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()`	Returns a string representation of the object.
`final void`	`wait()`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
`final void`	`wait(long timeoutMillis)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis, int nanos)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Constructor Details

VolatileCallSite

public VolatileCallSite(MethodType type)

Creates a call site with a volatile binding to its target. The initial target is set to a method handle of the given type which will throw an IllegalStateException if called.

Parameters:: type - the method type that this call site will have
Throws:: NullPointerException - if the proposed type is null

VolatileCallSite

public VolatileCallSite(MethodHandle target)

Creates a call site with a volatile binding to its target. The target is set to the given value.

Parameters:: target - the method handle that will be the initial target of the call site
Throws:: NullPointerException - if the proposed target is null

Method Details

getTarget

public final MethodHandle getTarget()

Returns the target method of the call site, which behaves like a volatile field of the VolatileCallSite.

The interactions of getTarget with memory are the same as of a read from a volatile field.

In particular, the current thread is required to issue a fresh read of the target from memory, and must not fail to see a recent update to the target by another thread.

Specified by:

getTarget in class CallSite

Returns:

the linkage state of this call site, a method handle which can change over time

See Also:

setTarget

public void setTarget(MethodHandle newTarget)

Updates the target method of this call site, as a volatile variable. The type of the new target must agree with the type of the old target.

The interactions with memory are the same as of a write to a volatile field. In particular, any threads is guaranteed to see the updated target the next time it calls getTarget.

Specified by:

setTarget in class CallSite

Parameters:

newTarget - the new target

Throws:

NullPointerException - if the proposed new target is null

WrongMethodTypeException - if the proposed new target has a method type that differs from the previous target

See Also:

dynamicInvoker

public final MethodHandle dynamicInvoker()

Produces a method handle equivalent to an invokedynamic instruction which has been linked to this call site.

This method is equivalent to the following code:

MethodHandle getTarget, invoker, result;
getTarget = MethodHandles.publicLookup().bind(this, "getTarget", MethodType.methodType(MethodHandle.class));
invoker = MethodHandles.exactInvoker(this.type());
result = MethodHandles.foldArguments(invoker, getTarget)

Specified by:: dynamicInvoker in class CallSite
Returns:: a method handle which always invokes this call site's current target

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