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:

• MutableCallSite

Constructor Summary

Constructors

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()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

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(MethodHandle)

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:

• getTarget()

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