VolatileCallSite

public class VolatileCallSite
extends CallSite

java.lang.Object
   ↳ java.lang.invoke.CallSite
     ↳ java.lang.invoke.VolatileCallSite


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.

In other respects, a VolatileCallSite is interchangeable with MutableCallSite.

See also:

Summary

Public constructors

VolatileCallSite(MethodType type)

Creates a call site with a volatile binding to its target.

VolatileCallSite(MethodHandle target)

Creates a call site with a volatile binding to its target.

Public methods

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.

Inherited methods

Public constructors

VolatileCallSite

added in API level 26
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 MethodType: the method type that this call site will have

Throws
NullPointerException if the proposed type is null

VolatileCallSite

added in API level 26
VolatileCallSite (MethodHandle target)

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

Parameters
target MethodHandle: the method handle that will be the initial target of the call site

Throws
NullPointerException if the proposed target is null

Public methods

dynamicInvoker

added in API level 26
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)
 

Returns
MethodHandle a method handle which always invokes this call site's current target

getTarget

added in API level 26
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.

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

setTarget

added in API level 26
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.

Parameters
newTarget MethodHandle: 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: