Documentation Version: 3.4 - Publication Date : Dec 24, 2014

ICondition

ICondition is the distributed implementation of the notify, notifyAll and wait operations on the Java object. You can use it to synchronize threads across the cluster. More specifically, you use ICondition when a thread's work depends on another thread's output. A good example can be producer/consumer methodology.

Please see the below code snippets for a sample producer/consumer implementation.

Producer thread:

HazelcastInstance hazelcastInstance = Hazelcast.newHazelcastInstance();
Lock lock = hazelcastInstance.getLock( "myLockId" );
ICondition condition = lock.newCondition( "myConditionId" );

lock.lock();
try {
  while ( !shouldProduce() ) {
    condition.await(); // frees the lock and waits for signal
                       // when it wakes up it re-acquires the lock
                       // if available or waits for it to become
                       // available
  }
  produce();
  condition.signalAll();
} finally {
  lock.unlock();
}

Consumer thread:

HazelcastInstance hazelcastInstance = Hazelcast.newHazelcastInstance();
Lock lock = hazelcastInstance.getLock( "myLockId" );
ICondition condition = lock.newCondition( "myConditionId" );

lock.lock();
try {
  while ( !canConsume() ) {
    condition.await(); // frees the lock and waits for signal
                       // when it wakes up it re-acquires the lock if 
                       // available or waits for it to become
                       // available
  }
  consume();
  condition.signalAll();
} finally {
  lock.unlock();
}