A sequence of primitive int-valued elements supporting sequential and parallel and aggregate operations. It is an int primitive specialization of Stream.

The Comparator is a comparison function in Java that imposes a total ordering on a collection of objects. The comparing is a static method in it

An RxJava Observable supports emitting a sequence of items. An Observer subscribes to an Observable. The Observer reacts to the items the Observable emits.

RxJava – Reactive Extensions for the JVM – a library for composing asynchronous and event-based programs using observable sequences for the Java VM.

The Abstract Factory Pattern provides an interface for creating families of related or dependent objects without specifying their concrete classes.

Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.

Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.