(If you want a refresher on arrays in Kotlin, kindly visit the first tutorial in this series.) In this section, we'll learn about the List, Set, and Map collections in Kotlin. To really understand the collections API in Kotlin, you'll need to be familiar with these basic classes and interfaces in Java. You can't see the implementation source code in Kotlin because the collections are actually implemented by the standard Java Collections such as ArrayList, Maps, HashMap, Sets, HashSet, List, and so on. You should note that these interfaces are linked to their implementation at compile time.
(We'll discuss interfaces in Kotlin in a future post.) Kotlin provides its collections API as a standard library built on top of the Java Collections API. We can retrieve, store, or organize the objects in a collection.
The main difference with the scheme used in Java is the absence of a containing annotation, which the Kotlin compiler generates automatically with a predefined name.Collections are used to store groups of related objects in memory. Java repeatable annotations are also supported from the Kotlin side. This will make it repeatable both in Kotlin and Java. To make your annotation repeatable, mark its declaration with the meta-annotation.
Just like in Java, Kotlin has repeatable annotations, which can be applied to a single code element multiple times. To avoid generating the TYPE_USE and TYPE_PARAMETER annotation targets, use the new compiler argument -Xno-new-java-annotation-targets. This is an issue for Android clients with API levels less than 26, which don't have these targets in the API. This is just like how the TYPE_PARAMETER Kotlin target maps to the .TYPE_PARAMETER Java target. If a Kotlin annotation has TYPE among its Kotlin targets, the annotation maps to .TYPE_USE in its list of Java annotation targets.
Ability to not generate JVM 1.8+ annotation targets
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