2.x: add missing <T> javadoc
2.x: add missing <T> javadoc
ReactiveX/RxJava,NiteshKant/RxJava,akarnokd/RxJava,AttwellBrian/RxJava,ReactiveX/RxJava,artem-zinnatullin/RxJava,reactivex/rxjava,reactivex/rxjava,artem-zinnatullin/RxJava,NiteshKant/RxJava,AttwellBrian/RxJava,akarnokd/RxJava