Kotlin ( a new programming language) for Android Development

Intro

Kotlin is a statically-typed programming language that runs on the Java Virtual Machine and also can be compiled to JavaScript source code or uses the LLVM compiler infrastructure. Its primary development is from a team of JetBrains programmers based in Saint Petersburg.

The name comes from Kotlin Island, near St. Petersburg. Andrey Breslav mentioned that the team decided to name it after an island just like Java was named after the Indonesian island of Java.

Google just announced that it will officially support Kotlin on Android as a “first-class” language.

Kotlin tools will be included with Android Studio 3.0 by default, and JetBrains and Google are pledging to support the language going forward. Kotlin as a language has a lot of similarities to Java in structure — it's object oriented and statically typed, and designed for similar problems Java solves. But because it's a clean slate in many ways, Kotlin adds a lot of nice-to-have features, a much cleaner syntax, ideas from functional programming, and other enhancements over Java.

Using Kotlin for Android Development

Kotlin is a great fit for developing Android applications, bringing all of the advantages of a modern language to the Android platform without introducing any new restrictions:

·         Compatibility: Kotlin is fully compatible with JDK 6, ensuring that Kotlin applications can run on older Android devices with no issues. The Kotlin tooling is fully supported in Android Studio and compatible with the Android build system.

·         Performance: A Kotlin application runs as fast as an equivalent Java one, thanks to very similar bytecode structure. With Kotlin's support for inline functions, code using lambdas often runs even faster than the same code written in Java.

·         Interoperability: Kotlin is 100% interoperable with Java, allowing using all existing Android libraries in a Kotlin application. This includes annotation processing, so databinding and Dagger work too.

·         Footprint: Kotlin has a very compact runtime library, which can be further reduced through the use of ProGuard. In a real application, the Kotlin runtime adds only a few hundred methods and less than 100K to the size of the .apk file.

·         CompilationTime: Kotlin supports efficient incremental compilation, so while there's some additional overhead for clean builds, incremental builds are usually as fast or faster than with Java.

·         Learning Curve: For a Java developer, getting started with Kotlin is very easy. The automated Java to Kotlin converter included in the Kotlin plugin helps with the first steps. Kotlin Koans offer a guide through the key features of the language with a series of interactive exercises.

Basic Syntax

Packages

A source file may start with a package declaration:

package foo.bar

fun baz() {}

class Goo {}

// ...

All the contents (such as classes and functions) of the source file are contained by the package declared. So, in the example above, the full name of baz() is foo.bar.baz, and the full name of Goo is foo.bar.Goo.

If the package is not specified, the contents of such a file belong to "default" package that has no name.

Default Imports

A number of packages are imported into every Kotlin file by default:

·         kotlin.*

·         kotlin.annotation.*

·         kotlin.collections.*

·         kotlin.comparisons.* (since 1.1)

·         kotlin.io.*

·         kotlin.ranges.*

·         kotlin.sequences.*

·         kotlin.text.*

Additional packages are imported depending on the target platform:

·         JVM:

o    java.lang.*

o    kotlin.jvm.*

·         JS:

o    kotlin.js.*

Kotlin Standard Library

The Kotlin Standard Library provides living essentials for everyday work with Kotlin. These include:

·         Higher-order functions implementing idiomatic patterns (let, apply, use, synchronized, etc).

·         Extension functions providing querying operations for collections (eager) and sequences (lazy).

·         Various utilities for working with strings and char sequences.

·         Extensions for JDK classes making it convenient to work with files, IO, and threading

Packages

kotlin	Core functions and types, available on all supported platforms.
kotlin.annotation	Library support for the Kotlin annotation facility.
kotlin.browser JS	Access to top-level properties (document, window etc.) in the browser environment.
kotlin.collections	Collection types, such as Iterable, Collection, List, Set, Map and related top-level and extension functions.
kotlin.comparisons	Helper functions for creating Comparator instances.
kotlin.concurrent JVM	Utility functions for concurrent programming.
kotlin.coroutines.experimental 1.1	Library support for coroutines, including support for lazy sequences.
kotlin.coroutines.experimental.intrinsics 1.1	Low-level building blocks for libraries that provide coroutine-based APIs.
kotlin.dom JS	Utility functions for working with the browser DOM.
kotlin.experimental 1.1	Experimental APIs, subject to change in future versions of Kotlin.
kotlin.io	IO API for working with files and streams.
kotlin.js JS	Functions and other APIs specific to the JavaScript platform.
kotlin.jvm JVM	Functions and annotations specific to the Java platform.
kotlin.properties	Standard implementations of delegates for delegated properties and helper functions for implementing custom delegates.
kotlin.ranges	Ranges, Progressions and related top-level and extension functions.
kotlin.reflect	Runtime API for Kotlin reflection
kotlin.reflect.full JVM 1.1	Extensions for Kotlin reflection provided by kotlin-reflectlibrary.
kotlin.reflect.jvm JVM	Runtime API for interoperability between Kotlin reflection and Java reflection provided by kotlin-reflect library.
kotlin.sequences	Sequence type that represents lazily evaluated collections. Top-level functions for instantiating sequences and extension functions for sequences.
kotlin.streams JVM 1.1 JRE8	Utility functions for working with Java 8 streams.
kotlin.system JVM	System-related utility functions.
kotlin.text	Functions for working with text and regular expressions.
org.khronos.webgl JS	Kotlin JavaScript wrappers for the WebGL API.
org.w3c.dom JS	Kotlin JavaScript wrappers for the DOM API.
org.w3c.dom.css JS	Kotlin JavaScript wrappers for the DOM CSS API.
org.w3c.dom.events JS	Kotlin JavaScript wrappers for the DOM events API.
org.w3c.dom.parsing JS	Kotlin JavaScript wrappers for the DOM parsing API.
org.w3c.dom.svg JS	Kotlin JavaScript wrappers for the DOM SVG API.
org.w3c.dom.url JS	Kotlin JavaScript wrappers for the DOM URL API.
org.w3c.fetch JS	Kotlin JavaScript wrappers for the W3C fetch API.
org.w3c.files JS	Kotlin JavaScript wrappers for the W3C file API.
org.w3c.notifications JS	Kotlin JavaScript wrappers for the Web Notifications API.
org.w3c.performance JS	Kotlin JavaScript wrappers for the Navigation Timing API.
org.w3c.workers JS	Kotlin JavaScript wrappers for the Web Workers API.
org.w3c.xhr JS	Kotlin JavaScript wrappers for the XMLHttpRequest API.

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