In Chapter 3, Reactive Streams, we discussed Publisher, which being the source of the data emits the data. RxJava is about the Observable Streams, hence it uses the name Observable instead of Publisher. The Observable is subscribed by the observer, which does consumption. The observer is usually called Subscriber. The observer or the subscriber reacts to the items or notification emitted by the Observable facilitating the operations without blocking. Keep in mind its Observable Streams, which means items can be data, an error, or stage of completion. Observable allows the execution of many instructions in parallel. Once all the instructions get processed their result is captured. You defined a mechanism for the transmission and ...

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