344      * Indicates that the caller is momentarily unable to progress, until the

   345      * occurrence of one or more actions on the part of other activities. By

   346      * invoking this method within each iteration of a spin-wait loop construct,

   347      * the calling thread indicates to the runtime that it is busy-waiting.

   348      * The runtime may take action to improve the performance of invoking

   349      * spin-wait loop constructions.

   350      * <p>

   351      * @apiNote

   352      * As an example consider a method in a class that spins in a loop until

   353      * some flag is set outside of that method. A call to the {@code onSpinWait}

   354      * method should be placed inside the spin loop.

   355      * <pre>{@code

   356      *     class EventHandler {

   357      *         volatile boolean eventNotificationNotReceived;

   358      *         void waitForEventAndHandleIt() {

   359      *             while ( eventNotificationNotReceived ) {

   360      *                 java.lang.Thread.onSpinWait();

   361      *             }

   362      *             readAndProcessEvent();

   363      *         }

   364      *

   365      *         void readAndProcessEvent() {

   366      *             // Read event from some source and process it

   367      *              . . .

   368      *         }

   369      *     }

   370      * }</pre>

   371      * <p>

   372      * The code above would remain correct even if the {@code onSpinWait}

   373      * method was not called at all. However on some architectures the Java

   374      * Virtual Machine may issue the processor instructions to address such

   375      * code patterns in a more beneficial way.

   376      * <p>

   377      * @since 9

   378      */

   379     @HotSpotIntrinsicCandidate

   380     public static void onSpinWait() {}

   381 

   382     /**