What is the difference between flatmap and switchmap in RxJava?

Question

The rxjava doc definition of switchmap is rather vague and it links to the same page as flatmap. What is the difference between the two operators?

Answer 1

Map, FlatMap, ConcatMap and SwitchMap applies a function or modifies the data emitted by an Observable.

• Map modifies each item emitted by a source Observable and emits the modified item.

• FlatMap, SwitchMap and ConcatMap also applies a function on each emitted item but instead of returning the modified item, it returns the Observable itself which can emit data again.

• FlatMap and ConcatMap work is pretty much same. They merge items emitted by multiple Observables and returns a single Observable.

• The difference between FlatMap and ConcatMap is the order in which the items are emitted.
• FlatMap can interleave items while emitting i.e the emitted items order is not maintained.
• ConcatMap preserves the order of items. But the main disadvantage of ConcatMap is, it has to wait for each Observable to complete its work thus asynchronous is not maintained.
• SwitchMap is a bit different from FlatMap and ConcatMap. SwitchMap unsubscribes from the previous source Observable whenever new item started emitting, thus always emitting the items from current Observable.