Taste Of Kotlin

What is Kotlin?

Kotlin is an OSS statically typed programming language that targets the JVM, Android, JavaScript and Native. It’s developed by JetBrains. The project started in 2010 and was open source from very early on. The first official 1.0 release was in February2016.

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.

Note: IntelliJ Java-to-Kotlin converter. Isn't perfect, it might have some issues. Which will be fixed in later updates.

Features:

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 to use 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. Compilation Time: 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.
Interoperability: Kotlin is fully compatible with all Java-based frameworks, which lets you stay on your familiar technology stack while reaping the benefits of a more modern language.

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.

So why is it perfect for android?

Android is stuck with Java 6 or 7 (depending on API)
Complete interoperability with Java
Compact runtime
We can do more with less code

Kotlin For Javascript

Kotlin provides the ability to target JavaScript. It does so by transpiling Kotlin to JavaScript.

Note: When you choose the JavaScript target, any Kotlin code that is part of the project as well as the standard library that ships with Kotlin is transpiled to JavaScript. However, this excludes the JDK and any JVM or Java framework or library used. Any file that is not Kotlin will be ignored during compilation.

Coding Conventions:

Naming Style: Is same as Java Coding Conventions such as,

use of camelCase for names (and avoid underscore in names)
types start with upper case
methods and properties start with lower case
use 4 space indentation
public functions should have documentation such that it appears in Kotlin Doc

Semicolons:

Kotlin provides semicolon inference: syntactically, subsentences (e.g., statements, declarations etc) are separated by the pseudo-token SEMI, which stands for (semicolon or newline). In most cases, there is no need for semicolons in Kotlin code.

Documenting Kotlin Code

The language used to document Kotlin code (the equivalent of Java's JavaDoc) is called KDoc. In its essence, KDoc combines JavaDoc's syntax for block tags (extended to support Kotlin's specific constructs) and Markdown for inline markup.

KDoc Syntax: Just like with JavaDoc, KDoc comments start with /** and end with */ . Every line of the comment may begin with an asterisk, which is not considered part of the contents of the comment.

Compairing Java and Kotlin code:

Hello, World in Java:

public class HelloWorld {
   public static void main(String[] args) {
  // Prints "Hello, World" in the terminal window.
      System.out.println("Hello, World");
   }
 }

Hello, World in Kotlin:

fun main(args: Array<String>){
   println("Hello, world")
}

You can clearly see the difference between these two.

Details is given in Summary tag. Check that out.

Another Sample:

class Foo(name: String) : Bar(name) {
    override fun makeStuff(): Stuff {
        return Stuff()
    }
}

That's all for now.

Books and website used for this code.

Websites:

Books:

Kotlin in Action
Kotlin, The Pragmatic Language For Android
Flexible Types in Kotlin
Kotlin Language Documentation
Programming Kotlin

While Writing Program

The fun keyword is used to declare a function. Programming in Kotlin is lots of fun,indeed!
The parameter type is written after the parameter name. This applies to variable declarations as well, as you’ll see later.
The function can be declared at the top level of a file; you don’t need to put it in a class.
Arrays are just classes. Unlike Java, Kotlin doesn’t have a special syntax for declaring array types.
You write println instead of System.out.println. The Kotlin standard library provides many wrappers around standard Java library functions, with more concise syntax, and println is one of them.
You can omit the semicolon from the end of a line, just as in many other modern languages.

In Summary:

Kotlin is statically typed and supports type inference, allowing it to maintain correctness and performance while keeping the source code concise.
Kotlin supports both object-oriented and functional programming styles, enabling higher-level abstractions through first-class functions and simplifying testing and multithreaded development through the support of immutable values.
It works well for server-side applications, fully supporting all existing Java frameworks and providing new tools for common tasks such as HTML generation and persistence.
It works for Android as well, thanks to a compact runtime, special compiler support for Android APIs, and a rich library providing Kotlin-friendly functions for common Android development tasks.
It’s free and open source, with full support for the major IDEs and build systems.
Kotlin is pragmatic, safe, concise, and interoperable, meaning it focuses on using proven solutions for common tasks, preventing common errors such as `NullPointerException`s,supporting compact and easy-to-read code, and unrestricted integration with Java.

Introduction to Kotlin Programming Language with Sample