public class ConstantCallSite extends CallSite
CallSitewhose target is permanent, and can never be changed. An
invokedynamicinstruction linked to a
ConstantCallSiteis permanently bound to the call site's target.
ConstantCallSitepublic ConstantCallSite(MethodHandle target)Creates a call site with a permanent target.
target- the target to be permanently associated with this call site
NullPointerException- if the proposed target is null
ConstantCallSiteCreates a call site with a permanent target, possibly bound to the call site itself.
During construction of the call site, the
createTargetHookis invoked to produce the actual target, as if by a call of the form
Note that user code cannot perform such an action directly in a subclass constructor, since the target must be fixed before the
The hook is said to bind the call site to a target method handle, and a typical action would be
someTarget.bindTo(this). However, the hook is free to take any action whatever, including ignoring the call site and returning a constant target.
The result returned by the hook must be a method handle of exactly the same type as the call site.
While the hook is being called, the new
ConstantCallSiteobject is in a partially constructed state. In this state, a call to
getTarget, or any other attempt to use the target, will result in an
IllegalStateException. It is legal at all times to obtain the call site's type using the
targetType- the type of the method handle to be permanently associated with this call site
createTargetHook- a method handle to invoke (on the call site) to produce the call site's target
WrongMethodTypeException- if the hook cannot be invoked on the required arguments, or if the target returned by the hook is not of the given
NullPointerException- if the hook returns a null value
ClassCastException- if the hook returns something other than a
Throwable- anything else thrown by the hook function
getTargetpublic final MethodHandle getTarget()Returns the target method of the call site, which behaves like a
finalfield of the
ConstantCallSite. That is, the target is always the original value passed to the constructor call which created this instance.
- Specified by:
- the immutable linkage state of this call site, a constant method handle
IllegalStateException- if the
ConstantCallSiteconstructor has not completed
- See Also:
setTargetpublic final void setTarget(MethodHandle ignore)Always throws an
UnsupportedOperationException. This kind of call site cannot change its target.
- Specified by:
ignore- a new target proposed for the call site, which is ignored
UnsupportedOperationException- because this kind of call site cannot change its target
- See Also:
dynamicInvokerpublic final MethodHandle dynamicInvoker()Returns this call site's permanent target. Since that target will never change, this is a correct implementation of