Kotlin top features overview
- 1. Sharing Café
- 2. Sharing Café WHAT IS KOTLIN? Kotlin is a Russian island between Saint Petersburg and the Gulf of Finland Kotlin is a programming language created by JetBrains
- 3. A FEW YEARS AGO… Sharing Café •It was in 2011 that JetBrains revealed the development of the Kotlin Project •One of the Kotlin Project goals was to compile as quickly as Java •Kotlin v1.0 was released in February 2015 •At Google I/O 2017 it was announced that Android is officially supporting Kotlin language •In November 2017 the v1.2 was released with a feature about sharing code between JVM and JavaScript platforms
- 4. SOME TOP FEATURES Sharing Café Extension function Higher-order function Destructuring declaration Singleton Null safety Allows you to write less code Inter-operable with Java
- 5. EXTENSION FUNCTION Sharing Café Provides the ability to extend a class with new functionality without having to inherit from the class or use any type of design pattern. Receiver type Receiver object Extension function are resolved statically, i.e. does not modify classes that they extend. They merely make new function callable with dot-notation.
- 6. HIGH-ORDER FUNCTION Sharing Café Function that takes functions as parameters, or returns a function. Function in Kotlin are first class, which means that they can be stored in variables and data structures, so that they can be passed as arguments to other high-order functions. outputConversion is a function that accept a function as argument with signature (Double) -> Double converterFunc can be celsiusToKelvin or celsiusToFahrenheit that are functions that accept a Double as argument and returns a Double. Function references
- 7. Sharing Café HIGH-ORDER FUNCTION - 2 Function can also be returned as a data type simply by declaring the type of the function as the return type
- 8. DESTRUCTURING DECLARATION Sharing Café This feature allows you to create multiple variables in one shot Can also be used with return value
- 9. SINGLETON Sharing Café It’s simple to define a Singleton. It is sufficient to use the keyword object which allows you to define an object which exists only as a single instance. Java way Kotlin way • object can’t have a constructor • init blocks are allowed if some initialization code is needed • init block will be executed lazily upon first access, in a thread-safe way
- 10. SINGLETON WITH COMPANION Sharing Café Kotlin does not have static keyword. How do we set static variables and methods? companion object is the equivalent to static objects in Java • companion object is common to all instances of the classes • Is initialized when the class is instantiated • Cannot be declared outside the class
- 11. NULL POINTER EXCEPTIONS Sharing Café I call it my billion-dollar mistake. It was the invention of null reference in 1965. - Tony Hoare
- 12. NULL SAFETY Sharing Café You need to say explicitly that a variable is nullable in order to be able to assign null to it. This can be accomplished using the ? operator • By default variables are declared as not nullable • To allow nulls we need to use the ? operator • ? operator can be used in safe cast
- 13. SO, TO CONCLUDE WE HAVE… Sharing Café 1. Kotlin increases productivity 2. Kotlin is ready for production • Increased readability • Includes modern features • Improved safety • So, we can focus on more important things • IntelliJ has parts written in Kotlin • Spring 5 introduces Kotlin support • TIOBE top 50 (41 position) • More than 150k devs use Kotlin