What are schedulers used for in the RxJava library?

Schedulers in RxJava are used to control on which thread or thread pool a particular part of the reactive stream will execute. This allows separating data work (e.g., loading from network or database) from UI updates, which is critical in Android.

Main tasks of schedulers:

• Define the thread for subscription (subscribeOn) — where the data source will run.
• Define the thread for observation (observeOn) — where results will be processed and transmitted.

Example:

Observable.just("data")
    .subscribeOn(Schedulers.io())          // loading in background thread
    .observeOn(AndroidSchedulers.mainThread()) // updating UI on main thread
    .subscribe(data -> textView.setText(data));