question: public void emitDirect ( int taskId , String streamId , Tuple anchor , List < Object > tuple ) { emitDirect ( taskId , streamId , Arrays . asList ( anchor ) , tuple ) ; }
target:  Emits a tuple directly to the specified task id on the specified stream. If the target bolt does not subscribe to this bolt using a direct grouping, the tuple will not be sent. If the specified output stream is not declared as direct, or the target bolt subscribes with a non-direct grouping, an error will occur at runtime. The emitted values must be immutable.