The bounds limit the concrete values of the type variable: We know this style of variance as declaration-site variance because we add the variance annotation while defining a generic class.įurther, we can constrain the type parameters in Scala by using type bounds. Similarly, we can use another variance annotation to make this generic class contravariant: class Garage Var myGarage: Garage = new Garage // This is still illegal Var myGarage: Garage = new Garage // This is legal now Let’s see how we can use the variance annotation to make our generic class covariant: class Garage Scala supports variance annotations of the generic classes’ type parameters to allow them to be covariant or contravariant. Val myGarage: Garage = new Garage // Illegal statement In simpler words, the following statement is illegal, even though it’s intuitive: val myGarage: Garage = new Garage // Illegal statement

Since the Garage class here takes a type as a parameter, we can create its instances with any type: class Vehicleīut, subtypes of a generic type in Scala are invariant by default. We can also use type parametrization to write generic classes in Scala. Kotlin itself is a very lightweight language, and it provides most of the advanced features like serialization and concurrency through extension libraries. While it started with JVM as the primary target platform, we can now quite easily compile the Kotlin source for other platforms, like JS and Native platforms. Kotlin also supports multi-platform programming, which may prove to be one of its key benefits. To help this cause, in 2019, Goggle announced Kotlin to be the preferred language for the Android platform! However, it maintains complete interoperability with Java, allowing for gradual adoption to build amongst the Java developer community. Petersberg in Russia.Īt heart, Kotlin is a multi-paradigm, object-oriented programming language that aims to be a better language than Java. While having very similar design goals as Scala, Kotlin targeted to improve the shortcomings of Scala - most notably, the slow compilation time of Scala.

JetBrains is the same company that has developed the popular IDE, IntelliJ IDEA. Kotlin is a relatively newer programming language, started by JetBrains in 2011.

Kotlin is null