80  *       arrives, an optional action is performed and the phase
  81  *       advances.  These actions are performed by the party
  82  *       triggering a phase advance, and are arranged by overriding
  83  *       method {@link #onAdvance(int, int)}, which also controls
  84  *       termination. Overriding this method is similar to, but more
  85  *       flexible than, providing a barrier action to a {@code
  86  *       CyclicBarrier}.
  87  *
  88  *   <li><b>Waiting.</b> Method {@link #awaitAdvance} requires an
  89  *       argument indicating an arrival phase number, and returns when
  90  *       the phaser advances to (or is already at) a different phase.
  91  *       Unlike similar constructions using {@code CyclicBarrier},
  92  *       method {@code awaitAdvance} continues to wait even if the
  93  *       waiting thread is interrupted. Interruptible and timeout
  94  *       versions are also available, but exceptions encountered while
  95  *       tasks wait interruptibly or with timeout do not change the
  96  *       state of the phaser. If necessary, you can perform any
  97  *       associated recovery within handlers of those exceptions,
  98  *       often after invoking {@code forceTermination}.  Phasers may
  99  *       also be used by tasks executing in a {@link ForkJoinPool}.
 100  *       Progress is ensured if the pool's parallelismLevel can
 101  *       accommodate the maximum number of simultaneously blocked
 102  *       parties.
 103  *
 104  * </ul>
 105  *
 106  * <p><b>Termination.</b> A phaser may enter a <em>termination</em>
 107  * state, that may be checked using method {@link #isTerminated}. Upon
 108  * termination, all synchronization methods immediately return without
 109  * waiting for advance, as indicated by a negative return value.
 110  * Similarly, attempts to register upon termination have no effect.
 111  * Termination is triggered when an invocation of {@code onAdvance}
 112  * returns {@code true}. The default implementation returns {@code
 113  * true} if a deregistration has caused the number of registered
 114  * parties to become zero.  As illustrated below, when phasers control
 115  * actions with a fixed number of iterations, it is often convenient
 116  * to override this method to cause termination when the current phase
 117  * number reaches a threshold. Method {@link #forceTermination} is
 118  * also available to abruptly release waiting threads and allow them
 119  * to terminate.
 120  *

  80  *       arrives, an optional action is performed and the phase
  81  *       advances.  These actions are performed by the party
  82  *       triggering a phase advance, and are arranged by overriding
  83  *       method {@link #onAdvance(int, int)}, which also controls
  84  *       termination. Overriding this method is similar to, but more
  85  *       flexible than, providing a barrier action to a {@code
  86  *       CyclicBarrier}.
  87  *
  88  *   <li><b>Waiting.</b> Method {@link #awaitAdvance} requires an
  89  *       argument indicating an arrival phase number, and returns when
  90  *       the phaser advances to (or is already at) a different phase.
  91  *       Unlike similar constructions using {@code CyclicBarrier},
  92  *       method {@code awaitAdvance} continues to wait even if the
  93  *       waiting thread is interrupted. Interruptible and timeout
  94  *       versions are also available, but exceptions encountered while
  95  *       tasks wait interruptibly or with timeout do not change the
  96  *       state of the phaser. If necessary, you can perform any
  97  *       associated recovery within handlers of those exceptions,
  98  *       often after invoking {@code forceTermination}.  Phasers may
  99  *       also be used by tasks executing in a {@link ForkJoinPool}.
 100  *       Progress is ensured if the pool's parallelism level can
 101  *       accommodate the maximum number of simultaneously blocked
 102  *       parties.
 103  *
 104  * </ul>
 105  *
 106  * <p><b>Termination.</b> A phaser may enter a <em>termination</em>
 107  * state, that may be checked using method {@link #isTerminated}. Upon
 108  * termination, all synchronization methods immediately return without
 109  * waiting for advance, as indicated by a negative return value.
 110  * Similarly, attempts to register upon termination have no effect.
 111  * Termination is triggered when an invocation of {@code onAdvance}
 112  * returns {@code true}. The default implementation returns {@code
 113  * true} if a deregistration has caused the number of registered
 114  * parties to become zero.  As illustrated below, when phasers control
 115  * actions with a fixed number of iterations, it is often convenient
 116  * to override this method to cause termination when the current phase
 117  * number reaches a threshold. Method {@link #forceTermination} is
 118  * also available to abruptly release waiting threads and allow them
 119  * to terminate.
 120  *