Guava MultiMap and ConcurrentModificationException [duplicate]

Answer 1

I prefer Multimap.values().iterator() if you don't care about the key. You should also try to stay away from using synchronized blocks as much as possible, because you cannot prioritize reads/writes effectively.

ReadWriteLock lock = new ReentrantReadWriteLock();
Lock writeLock = lock.writeLock(); 

public void removeCommands(Command value) {
  try {
    writeLock.lock();
    for (Iterator it = multiMap.values().iterator(); it.hasNext();) {
      if (it.next() == value) {
        it.remove();
      }
    }
  } finally {
    writeLock.unlock();
  }
}