1.Program struct:
$ root/
`--rx
|--annotations -->注解
| |--Beta.java
| `--Experimental.java
|--exceptions -->异常
| |--CompositeException
| |--Exception
| |--MissingBackpressureException
| |--OnCompletedFailedException
| |--OnErrorFailedException
| |--OnErrorNotImplementedException
| |--OnErrorThrowable
| `--UnsubscribeFailedException
|--functions
|--internal
| |--atomic ---->开源框架JCTools，处理并发操作
| |--unsafe -/
|--observables
|--obserbers
|--plugins
|--schedulers
|--singles
|--subjects
|--subscriptions
|--Notification.java
|--Observable.java
|--Observer.java
|--Producer.java
|--Scheduler.java
|--Single.java
|--SingleSubscribler.java
|--Subscriber.java
`--Subcription.java