Java compact1, compact2, compact3 java.lang.invoke Class VolatileCallSite（JDK8）

Constructor Detail

• 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 Detail

• 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(java.lang.invoke.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