Programming Kotlin

Sequences for Lazy Evaluation

Simply put, collections are eager and sequences are lazy. Sequences are optimized wrappers around collections intended to improve performance. In this section, we’ll look at what that means and how to decide when to use collections and when to use sequences.

Unlike Java, the methods like filter(), map(), and so on are available in Kotlin directly on collections like List<T>, instead of only on a Stream<T>. The designers of Java made a decision against offering these methods on collections for performance reasons. The designers of Kotlin, on the other hand, decided to lean toward convenience, and they expect us to choose wisely.

Use the internal iterators on collections directly in Kotlin when the collection size ...