question: private < T > ForkJoinTask < T > externalSubmit ( ForkJoinTask < T > task ) { Thread t ; ForkJoinWorkerThread w ; WorkQueue q ; Objects . requireNonNull ( task ) ; if ( ( ( t = Thread . currentThread ( ) ) instanceof ForkJoinWorkerThread ) && ( w = ( ForkJoinWorkerThread ) t ) . pool == this && ( q = w . workQueue ) != null ) q . push ( task ) ; else externalPush ( task ) ; return task ; }
target:  Pushes a possibly-external submission.