Java vs Kotlin continued:

The Kotlin language avoids checked exception. This makes it easier to write code without special handlers. 

Ranges and progressions are easy to implement with Kotlin. For example, ascending can be specified as say 1..4 and descending can be specified as 4 downTo 1. Ranges include the sentinel values and are defined for comparable types that have an order. It is usually called in its operator form such as Number(1)..Number(4)

Collections are another example of Kotlin improvements. Kotlin collections allow us to manipulate a number of objects independently of the exact type of objects stored in them. Objects in a collection are called elements or items. The collections represented by Set, Map and List continue to hold the same relevance in Kotlin. The interfaces and related functions to access these are located in the kotlins.collections package

Kotlin collection types come with a standard pair of interfaces represented by 1) a read-only interface and a 2) mutable interface where the latter extends the former with write operations. All write operations modify the same mutable collection object, so the reference doesn’t change.

The read-only collection types are covariant where collections of base types can be used to pass around collections of derived types. Mutable collections are not covariant because the type safety cannot be enforced.

Collection<T> is the interface at the top level for read-only collection which includes retrieving size, checking item membership and others. All Collections are iterable.

Along with Collections, the Kotlin standard library comes with sequences. Sequences are like iterables but they are not processed eagerly. Instead they are processed lazily when the result of the chain is required. Sequences perform all the operations on one item at a time while iterable completes each step for the collection and then proceeds to the next step.