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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

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 package java.lang.invoke;

 /**

  * A {@code VolatileCallSite} is a {@link CallSite} whose target acts like a volatile variable.

  * An {@code invokedynamic} instruction linked to a {@code 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.

  * <p>

  * Unlike {@code MutableCallSite}, there is no

  * {@linkplain MutableCallSite#syncAll syncAll operation} on volatile

  * call sites, since every write to a volatile variable is implicitly

  * synchronized with reader threads.

  * <p>

  * In other respects, a {@code VolatileCallSite} is interchangeable

  * with {@code MutableCallSite}.

  * @see MutableCallSite

  * @author John Rose, JSR 292 EG

  */

 public class VolatileCallSite extends CallSite {

     /**

      * 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 {@code IllegalStateException} if called.

      * @param type the method type that this call site will have

      * @throws NullPointerException if the proposed type is null

      */

     public VolatileCallSite(MethodType type) {

         super(type);

     }

     /**

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

      * The target is set to the given value.

      * @param target the method handle that will be the initial target of the call site

      * @throws NullPointerException if the proposed target is null

      */

     public VolatileCallSite(MethodHandle target) {

         super(target);

     }

     /**

      * Returns the target method of the call site, which behaves

      * like a {@code volatile} field of the {@code VolatileCallSite}.

      * <p>

      * The interactions of {@code getTarget} with memory are the same

      * as of a read from a {@code volatile} field.

      * <p>

      * 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.

      *

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

      * @see #setTarget

      */

     @Override public final MethodHandle getTarget() {

         return getTargetVolatile();

     }

     /**

      * 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.

      * <p>

      * 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 {@code getTarget}.

      * @param newTarget the new target

      * @throws NullPointerException if the proposed new target is null

      * @throws WrongMethodTypeException if the proposed new target

      *         has a method type that differs from the previous target

      * @see #getTarget

      */

     @Override public void setTarget(MethodHandle newTarget) {

         checkTargetChange(getTargetVolatile(), newTarget);

         setTargetVolatile(newTarget);

     }

     /**

      * {@inheritDoc}

      */

     @Override

     public final MethodHandle dynamicInvoker() {

         return makeDynamicInvoker();

     }

 }