Introduction to Kotlin
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Introduction to Kotlin

Learn Kotlin, a modern language for the JVM (now officially supported on Android!)
4.3 (69 ratings)
Instead of using a simple lifetime average, Udemy calculates a course's star rating by considering a number of different factors such as the number of ratings, the age of ratings, and the likelihood of fraudulent ratings.
319 students enrolled
Created by Dmitri Nesteruk
Last updated 6/2017
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  • 5 hours on-demand video
  • 16 Supplemental Resources
  • Full lifetime access
  • Access on mobile and TV
  • Certificate of Completion
What Will I Learn?
  • Solve problems in Kotlin
  • Understand Kotlin's advantages over Java
  • Effectively leverage Kotlin's null safety and mutability guarantees
  • Speed up work with collection using Kotlin's collection operationrs
  • Have fun with a new JVM language!
View Curriculum
  • A basic knowledge of Java is beneficial

This is a course on the Kotlin programming language. This course is designed for people already familiar with Java who are looking for a more modern, expressive and powerful language for the JVM.

In this course, you will learn about:

  • How to install and run Kotlin and why toolability matters
  • Type inference and how it can save you a lot of time
  • Smart control flow structures that let you write more succinctly
  • Mutability options (val and var), what they mean and how to use them
  • Nullability guarantees and how they make your code more safe
  • The power of functional literals (nested functions and lambdas)
  • Powerful built-in delegation functionality
  • How to leverage Kotlin's collection operations to process data sets efficiently

... and a lot more!

This course is completely live-demo based. All the lectures are examples of real code being edited and executed using the IntelliJ IDEA Community Edition IDE.

Update: Google has just announced official support for Kotlin on Android. Congratulations to the Kotlin team!

Who is the target audience?
  • Android developers wishing to learn the latest Google-approved language
  • Java developers looking for a better programming language
  • Developers looking for interesting language design ideas
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Curriculum For This Course
54 Lectures
Introduction to Kotlin
3 Lectures 10:24

A brief overview of why Kotlin is so good.

Preview 04:28

A little note about the options available for downloading and installing Kotlin.

Preview 02:03

Let's set up the IDE and run our first Kotlin program.

Preview 03:53
Types and Variables
5 Lectures 29:07

Learn about the difference between val and var. Also: there is no new and no semicolons.

Variable Declarations

Thanks to type deduction, most variable type decorations are not necessary. Woo-hoo!

Type Inference

Ranges of values. Self-explanatory, right?


A look at how arrays are represented and used in Kotlin.


Strings aren't complicated, but interpolation makes them more powerful.

Strings and String Interpolation
Control Flow
5 Lectures 22:56

Kotlin provides powerful support for dealing with nullability. Lean everything about ?, ?., ?: and !!


Yer olde if is an expression that can return values and can appear in interpolated strings.

If Statement

Why should the IDE check if you are risking an NPE, if the compiler can do it just as well? This awesome compiler feature also takes care of type conversions and more.

Smart Casts

This ain't your father's for loop!

For Iteration

Kotlin's powerful alternative to Java's switch.

When Expression
5 Lectures 18:05

Kotlin has functions which are not inside any class. What is this, C++?!?

Top-Level Functions

Kotlin supports default argument values and calls with named arguments.

Return Types and Arguments

Call a function with any number of arguments, comma-separated-like.

Variable-Argument Functions

Functions within functions.

Local (a.k.a. Nested or Inner) Functions

Explains how functions such as downTo are implemented.

Infix Functions
Lambda Functions
4 Lectures 15:39

Yay, lambdas! Oh, wait, Java has lambdas too? Yeah, but not like these!

Warning: Kotlin lambdas may or may not be cached when passed into Java event listeners. Be careful!

Lambda Functions

Functions taking functions, but why?

Higher-Order Functions

Define the context of the function's operation. Advanced topic!

Function Types with Receivers

Give a class a magic method called invoke and call it like a function (a.k.a. functor).

10 Lectures 46:27

What, no fields? With Kotlin, forget about fields and getter/setter hell: properties take care of it all!


Give any type additional functionality.

Extension Functions and Properties

Primary constructors provide an epic level of succinctness. But if you need to do more than initialize some fields, init block to the rescue!

Primary Constructors and Initialization

You can override the implementation of a property in an external class. But why?!?

Warning: when you reference this in a delegated property class, you are referring to that class, not the class where the delegated property is going to be used. Be careful!

Delegated Properties

Simple, yet powerful, data classes auto-implement the basic scaffolding for you. Don't worry, you can override anything you don't like!

Data Classes

Kotlin lets you make Singletons with ease. It doesn't have static functions, but companion objects are a close alternative.


Kotlin doesn't have statics. But you can still get them, in a way.

Companion Objects

Learn about the override keyword, base call disambiguation, opening types and more.


Interfaces... can contain properties as well as functions.


The Decorator pattern is essentially built-in in Kotlin.

Class Delegation
Collection Operations
12 Lectures 01:33:15

A discussion of Kotlin collection support and why it rocks.

Preview 02:18

Let's dig into kotlin-runtime.jar and find all the classes related to collection operations as well as sequences. We'll also learn how to make sequence generators: a useful feature that we'll use throughout this entire section.

API Overview and Sequence Generators

Counting how many elements fit a predicate.

Quantifiers (any, all, count, contains)

Mapping each element to something else.

Projection (map, flatMap, associate)

Compressing a sequence to a single value.

Aggregation (fold, reduce, joinToString)

Keeping elements satisfying (or not) a particular predicate and throwing all others away.

Filtering (filter, filterNot)

Splitting a sequence based on a criterion.

Partitioning (drop & take)

Grouping elements by a particular key.

Grouping (groupBy)

Sorting a data set by one or more of its properties.

Sorting (sortedBy, sortedWith, compareBy, thenBy)

Operations which try to access an individual element of the collection.

Element Operations (first, last, single, elementAt)

Operations on algebraic sets.

Set Operations (distinct, intersect, union, subtract)

A summary of all the collection operations we've discussed in this section of the course.

5 Lectures 30:06

Yeah, Java has reflection too, but can you tell if your object is a singleton or a companion object? Of course not. Kotlin reflection to the rescue!

Class Reflection

Learn to work with references to functions. Remember, functions are everywhere in kotlin. Got a property? Well, its getters/setters are functions. Also you get to see how to handle references to function overloads.

Function References

Learn to work with property references. Remember, typical val/var declarations are properties too!

Property References

Learn to work with references to class constructors.

Constructor References

Function and property references can also bind itself to an instance of the receiver.

Bound References
Odds & Ends
5 Lectures 29:23

Type aliases provide alternative names for existing types.

Type Aliases

Yes, enumerations, with abstract functions and whatnot.


Kotlin has no checked exceptions. But try-catch is an expression.


But only standard operators, none of that F#-inspired operator <#%$> magic.

Operator Overloads

A look at how function types with receivers, together with lambda expressions, can help us make Groovy-style builders.

Type-Safe Builders
About the Instructor
Dmitri Nesteruk
4.5 Average rating
1,033 Reviews
10,458 Students
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Quant Finance • Algotrading • Software/Hardware Engineering

Dmitri Nesteruk is a developer, speaker and podcaster. His interests lie in software development and integration practices in the areas of computation, quantitative finance and algorithmic trading. His technological interests include C#, F# and C++ programming as well high-performance computing using technologies such as CUDA. He has been a C# MVP since 2009.

Dmitri is a graduate of University of Southampton (B.Sc. Computer Science) where he currently holds a position as a Visiting Researcher. He is also an instructor on an online intro-level Quantitative Finance course, and has also made online video courses on CUDA, MATLAB, D, the Boost libraries and other topics.