kotlin-core-api

To use mapNotNull on a Kotlin collection, apply it to transform elements while automatically excluding null results, yielding a non-nullable list. This standard library function iterates each element, applies the transformation, and collects only non-null outputs.

The best way to transform large Kotlin collections is using sequences for lazy evaluation. Sequences process elements one at a time through the chain, avoiding intermediate list allocations and significantly reducing memory overhead for large datasets.

Kotlin reflection works through the kotlin.reflect API to inspect classes, properties, and functions at runtime. You retrieve KClass references and use KProperty instances to dynamically access property names, types, and values without compile-time knowledge.

Yes, the Kotlin standard library includes built-in testing assertions via kotlin.test. This framework provides basic assertion functions like assertEquals, assertTrue, and assertNotNull to validate expected outcomes directly within your test functions.

You need Kotlin scope functions like let, run, with, apply, and also to execute code blocks within an object's context. They differ by returning the context object or the block result, enabling concise initialization and chained operations.