cast()

A simple, map-like operator to cast each emission to a different type is cast(). If we want to take Observable<String> and cast each emission to an object (and return an Observable<Object>), we could use the map() operator like this:

Observable<Object> items = 
  Observable.just("Alpha", "Beta", "Gamma").map(s -> (Object) s);

But a shorthand we can use instead is cast(), and we can simply pass the class type we want to cast to, as shown in the following code snippet:

Observable<Object> items = 
  Observable.just("Alpha", "Beta", "Gamma").cast(Object.class);

If you find that you are having typing issues due to inherited or polymorphic types being mixed, this is an effective brute-force way to cast everything down to a common base type. But strive to properly use generics and type wildcards appropriately first.