question: public static String mkStreamId ( String jobId , String opletId , int oport ) { Objects . requireNonNull ( jobId , "jobId" ) ; Objects . requireNonNull ( opletId , "opletId" ) ; if ( oport < 0 ) throw new IllegalArgumentException ( "oport" ) ; return String . format ( STREAMID_FMT , jobId , opletId , oport ) ; }
target:  Make a streamId for the specified stream.