# Common Classes

- [rx.Observable](https://github.com/Netflix/RxJava/blob/master/rxjava-core/src/main/java/rx/Observable.java)
- [rx.Observer](https://github.com/Netflix/RxJava/blob/master/rxjava-core/src/main/java/rx/Observer.java)
- [rx.Subscription](https://github.com/Netflix/RxJava/blob/master/rxjava-core/src/main/java/rx/Subscription.java)
- [rx.Scheduler](https://github.com/Netflix/RxJava/blob/master/rxjava-core/src/main/java/rx/Scheduler.java)