Rxjava链接多个请求

我对RxJava的概念是新的。 我想联系一些电话：

Observable<RoomList> listRoomsCall = mRoomServiceApi.listRooms();

我应该如何将第一个呼叫与下一个呼叫连接起来

我想我应该使用

flatMap

和循环来调用所有请求，但最后如何连接所有响应

  listRoomsCall.flatMap(v -> {
            for (ExchangeRoom exchangeRoom : v.getExchangeRoomList()) {
               mMeetingServiceApi.listMeetings(roomID, startsAtString, endsAtString, free);
            }
        })

---

再次将内部列表变为可观察的

和
flatMap
：

listRoomsCall
.flatMapIterable(v -> v.getExchangeRoomList())
.flatMap(exchangeRoom -> {
    mMeetingServiceApi.listMeetings(roomID, startsAtString, endsAtString, free);
})
.subscribe(/* */);

或

listRoomsCall
.flatMapIterable(v -> v.getExchangeRoomList())
.flatMap(exchangeRoom -> {
    mMeetingServiceApi.listMeetings(roomID, startsAtString, endsAtString, free);
})
.subscribe(/* */);

listRoomsCall
.flatMap(v -> 
     Observable.fromIterable(v.getExchangeRoomList())
     .flatMap(exchangeRoom -> {
         mMeetingServiceApi.listMeetings(roomID, startsAtString, endsAtString, free);
     })
)
.subscribe(/* */);