public SharedDataIteratorSource(Object identifier,ISourceDataIteratorProvider<T> sourceDataIteratorProvider,long timeToLive){
  if (sourceDataIteratorProvider == null)   throw new IllegalArgumentException("sourceDataIteratorProvider cannot be null");
  _identifier=identifier;
  _sourceDataIteratorProvider=sourceDataIteratorProvider;
  _timeToLive=timeToLive;
  _createdTime=SystemTime.timeMillis();
}

public SharedDataIteratorSource ( Object identifier , ISourceDataIteratorProvider < T > sourceDataIteratorProvider , long timeToLive ) { if ( sourceDataIteratorProvider == null ) throw new IllegalArgumentException ( "sourceDataIteratorProvider cannot be null" ) ; _identifier = identifier ; _sourceDataIteratorProvider = sourceDataIteratorProvider ; _timeToLive = timeToLive ; _createdTime = SystemTime . timeMillis ( ) ; }
construct a new source
