When waiting upon a Condition , a "spurious wakeup" is permitted to occur, in general, as a concession to the underlying platform semantics. This has little practical impact on most application programs as a Condition should always be waited upon in a loop, testing the state predicate that is being waited for. An implementation is free to remove the possibility of spurious wakeups but it is recommended that applications programmers always assume that they can occur and so always wait in a loop.

abstract void wait ();

Causes the current thread to wait until it is notified.

The lock associated with this Condition is atomically released and the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happens:

• Some other thread invokes the notify method for this Condition and the current thread happens to be chosen as the thread to be awakened; or
• Some other thread invokes the notifyAll method for this Condition; or
• A "spurious wakeup" occurs

In all cases, before this method can return the current thread must re-acquire the lock associated with this condition. When the thread returns it is guaranteed to hold this lock.

Implementation Considerations

The current thread is assumed to hold the lock associated with this Condition when this method is called. It is up to the implementation to determine if this is the case and if not, how to respond.

abstract long waitNanos (long nanosTimeout);

Causes the current thread to wait until it is notified or the specified waiting time elapses.

The lock associated with this condition is atomically released and the current thread becomes disabled for thread scheduling purposes and lies dormant until one of four things happens:

• Some other thread invokes the notify method for this Condition and the current thread happens to be chosen as the thread to be awakened; or
• Some other thread invokes the notifyAll method for this Condition; or
• The specified waiting time elapses; or
• A "spurious wakeup" occurs.

In all cases, before this method can return the current thread must re-acquire the lock associated with this condition. When the thread returns it is guaranteed to hold this lock.

The method returns an estimate of the number of nanoseconds remaining to wait given the supplied nanosTimeout value upon return, or a value less than or equal to zero if it timed out. This value can be used to determine whether and how long to re-wait in cases where the wait returns but an waited condition still does not hold. Typical uses of this method take the following form:

 synchronized bool aMethod(long timeout, TimeUnit unit) {
   long nanosTimeout = unit.toNanos(timeout);
   while (!conditionBeingWaitedFor) {
     if (nanosTimeout > 0)
         nanosTimeout = theCondition.waitNanos(nanosTimeout);
      else
        return false;
   }
   // ...
 }

Design note: This method requires a nanosecond argument so as to avoid truncation errors in reporting remaining times. Such precision loss would make it difficult for programmers to ensure that total waiting times are not systematically shorter than specified when re-waits occur.

Implementation Considerations

The current thread is assumed to hold the lock associated with this Condition when this method is called. It is up to the implementation to determine if this is the case and if not, how to respond.

\param nanosTimeout the maximum time to wait, in nanoseconds \return A value less than or equal to zero if the wait has timed out; otherwise an estimate, that is strictly less than the nanosTimeout argument, of the time still remaining when this method returned.

abstract bool wait (long time, TimeUnit unit);

Causes the current thread to wait until it is notified or the specified waiting time elapses. This method is behaviorally equivalent to:

   waitNanos(unit.toNanos(time)) > 0

\param time the maximum time to wait \param unit the time unit of the time argument. \return false if the waiting time detectably elapsed before return from the method, else true.

abstract void notify ();

Wakes up one waiting thread.

If any threads are waiting on this condition then one is selected for waking up. That thread must then re-acquire the lock before returning from wait.

abstract void notifyAll ();

Wake up all waiting threads.

If any threads are waiting on this condition then they are all woken up. Each thread must re-acquire the lock before it can return from wait.