Kotlin: Master Kotlin Programming - Step by Step Guide!

Creating pure functions to solve simple problems

• Learn basic Kotlin syntax

• Create functions with no arguments

• Create functions with arguments

Understanding difference between pure functions and functions with side effects

• Create global state

• Create functions that interact with global state

• Understand the behavior of functions with side effects

Mutable data - source of side effects. Reducing amount of side effects by using immutable data classes

• Learn Kotlin data classes syntax

• Create immutable data class

• Use copy constructor to modify immutable data

Using recursive functions to solve problems

• Understand recursion

• Break problem into 2 small ones

• Implement recursive algorithm

Generating Fibonacci number by given position

• Understand problem

• Implement solution using recursion

• Test solution

Statically typed code is hard to reuse. Generics makes statically typed code reusable.

• Learn Kotlin syntax for Generics.

• Implement simple data wrapper without generics

• Implement improved data wrapper using generics

How to create function without name in Kotlin? Using lambda expression

• Learn Kotlin syntax for lambda expressions

• Create lambda and assigning it to variable

• Understand lambda type signatures

How could we pass functions to another function? Yes using higher-order functions

• Learn Kotlin syntax for higher-order functions

• Create function that access function as argument

• Create function that returns function as argument

How to delay execution until result is needed. Using lazy evaluation.

• Create ordinary function that accept ready to use arguments

• Improve the function using lambda expressions

• Implement sequence generator using lazy evaluation technics

How to create lambda from named function. Using function reference

• Create lambda expression from maned function manually

• Create lambda expression from named function using function reference

• Use function reference in combination with higher-order functions

How to add properties to existing functions. Using Monads.

• Understand requirements for Monad.

• Create simple monad container

• Explore Optional monad from JDK

How to return multiple arguments from function. Using destructive declaration

• Create and destructing Pair object

• Destruct Pair in lambda expressions

• Create classes that supports destruction

How to reduce number of arguments of a function - by using partial application

• Understand use case

• Implement straight forward approach

• Implement reusable extension function

How to express function with multiple arguments only by functions with one argument - using curried functions

• Understand use case

• Implement straight forward approach

• Implement reusable extension function

How to glue two functions together - using forward compose operation

• Understand use case

• Implement straight forward approach

• Implement reusable extension function

How do we store data in list, using functional programming principles

• Understand structure of functional list

• Implement list

• Create and use list

How to make implementation of functional list useful, by adding more operators

• Define list of operators we want to implement

• Implement Operators using recursion

• Use implemented operators together

How we could create restricted classes hierarchy in Kotin - by using sealed classes

• Feature syntax description

• Look into use cases Use cases

• Use with when operator

How we do branching by complex conditions - by using pattern matching techniques

• Describe pattern matching

• Describe Kotlin limitations

• Go through examples

Refresh what we’ve learned so far

• Create small functions

• Use functional programming techniques

• Improve your code by using advanced Kotlin features

How to make concurrent programming easier - by using coroutines.

• What is coroutines

• Create the project with kotlinx.coroutines library

• Use coroutines

Many of basic functional components are not included in standard library

• Library description

• Exploring Arrow website

• Going through available library modules

How to use simple Monads

• Creating project

• Adding Arrow library dependency

• Going through examples of using Option, Either and Ior monads

How we could manage side effects in functional programming - by using IO monad

• Monad description

• Monad creation

• Handle successful execution and failure

How do we use DI pattern in functional style - by using Reader Monad

• Monad description

• Monad creation

• Go through operators

How we could manage side effects in functional programming - by using IO monad

• Monad description

• Monad creation

• Handle successful execution and failure

How do we design our app to leverage functional concepts

• Describe JavaFx

• Describe unidirectional data flow concept

• Design high level components

How do we make JavaFx, Arrow and coroutines work together

• Checkout project using git

• Implement await extension function for IO monad

• Use IO Monad inside coroutines

How do we start implementing our app - by designing interfaces of our components

• Introduce middleware in initial design

• Showcase UI and functional of the app

• Create interfaces

How do we make our components work

• Implement UI

• Implement state

• Implement logic

How to glue this components together

• Instantiate components

• Late binding

• Handle user actions

To do we ensure this components works correctly - by writing tests

• Write tests for reducer

• Write tests for store

• Write tests for middleware

Functions can be overly long with additional unnecessary scaffolding. That makes it more difficult to understand what the code is doing. The goal here is to reduce the code to a single line.

• Check the function body for conversion

• Replace a block body with an expression body

• Verify that the function is two lines or less

If cascades can be unnecessarily long with scaffolding, which takes time to understand the code. Replace ifwith when.

• Replace a block body with an expression body

• Convert an if cascade to a when expression

• Verify when the expression runs with no errors

Often when calling a function, the parameters lack detail. Also, overloaded functions can result in a lot of unnecessary duplicated code. Use named arguments to add parameter info and default parameters to reduce the number of overloaded functions.

• Add named arguments to the function

• Add default parameters to the function

• Verify that the amended function works with a different number of parameters

Adding functionality to a class can be a sizable task involving inheriting a new class. Adding an extension function allows more functionality to be added with creating an inherited class.

• Define an extensional function

• Call the extension function

• Verify that there are no syntax errors and the code runs with the expected result

It is common that, after creating a class instance, a number of methods of the object will need to be called. That means the object named will be called a number of times. By using a number of scoping methods, the references to object names can be removed.

• Add a with function to remove object names

• Use the apply extension for method initialization

• Successful calls of with and apply functions, with the expected result

Null pointer exceptions can be catastrophic for applications. Kotlin methods will be provided for removing null pointer exceptions in a graceful and concise manner.

• Use the Elvis operator for handling nulls in a concise manner

• Use Smart Cast to remove ClassCastException

• Run the code to verify solutions and remove the exceptions

Using the standard If condition to check for null makes the code verbose and unnecessarily long. A solution will be provided for handling the null expression in a clearer, more concise way.

• Replace the If condition with let to make your code more concise

• Combine let with Elvis for returning default values

• Run the code and confirm that let returns same result

Removing null elements from a collection is a common situation. But this can involve several operations, making code long, verbose, and open to errors. Provide solutions for removing null elements which are concise and clear.

• Apply filterNotNull for removing nulls from a collection

• Use the listOfNotNull function to create a null-free collection

• Run the code for both solutions to confirm that lists have no nulls

When an object is shared between different threads, its data can be corrupted if the threads try to access it at the same time. Provide solutions to control access to the shared object from multiple threads.

• Add the synchronized function to the thread definitions

• Replace this function with the Reentrant withLock extension function

• Check both solutions and maintain BasicThreadOne access of the shared object

Using a class instance for shared data between multiple threads will cause problems if more than one instance is created. Use a singleton to create a single instance of a class.

• Run the class code to confirm multiple list instances

• Replace the class with the object singleton

• Run the singleton code to check for single list

Classes can consist of multiple constructors, which tend to be verbose and take time for the reader to absorb. Provide a method of initializing classes’ properties in a single line, making the code concise.

• Implement a primary constructor for initializing properties

• Initialize the properties inside the primary constructor parenthesis

• Run the code to check whether the class properties are initialized

Extending a framework class with multiple constructors can be complex and difficult. Provide the Kotlin recommended approach for extending a class with multiple constructors.

• Describe how to implement secondary constructors

• Describe how to pass secondary constructor parameters to the super constructor

• Run code to check whether the super constructor properties are initialized

When providing additional logic to a property that stores a value, recursion can occur, resulting in an exception. Provide a solution to remove recursion issues.

• Provide a backing field to the property getter

• Provide a backing field to the property setter

• Run code to test that recursion has been removed

Creating a sub-class which will be used in a localized place involved an additional amount of code. Provide an alternative solution to using a sub-class.

• Use an object expression to create an anonymous object

• Override the superclass method in the anonymous constructor

• Start the thread to verify that the overridden method executes

When using a class with multiple secondary constructors, additional code will be required for creating instances of the class. Provide an alternative solution to creating class instances using multiple constructors.

• Replace secondary constructors with primary constructor and companion object

• Add a factory pattern to the companion object

• Verify that the factory methods provide the same result as secondary constructors

Using traditional functions can result in unnecessary, similar code. Find an alternative method to defining and calling functions.

• Replace the function call with a lambda

• Add a function type to the lambda result

• Run code to verify that the result is same as the original

Java does not support passing a function to another function as an argument. Find a solution where a function can be passed to another function.

• Create a function with a function type as its parameter

• Replace the function argument with a lambda expression

• Call the function type parameter from inside the function

There can be confusion between read-only versus immutable collections related to thread safety. Create code to check read-only and immutable collections for thread safety.

• Write code that checks if read-only contents can be modified

• Write code that checks if immutable contents can be modified

• Run code to identify which collection is thread-safe

Filtering and modifying the contents of a collection are common operations. Find Kotlin solutions to simplify this.

• Implement the Kotlin filter extension function

• Implement the Kotlin map extension function

• Run code for both functions and check the result collection

The class toString, equals, and hashCode methods are very common methods. But they need to be implemented manually, which involves a lot of additional boilerplate code. Find an alternative method to simplify the creation of the toString, equals, and hashCode methods.

• Manually create toString, equals, and hashCode methods to illustrate effort

• Replace manual methods with the data class

• Run code using the data class to verify the same output

There are a number of functions available which can provide the same result. But the time taken to complete the operation may not be the same. Find the method for recording the time taken for executing a function. Find a way of generating the equivalent Java code to help identify any potential performance issues.

• Use the measureTimeMillis function to record elapsed time

• Use Kotlin Bytecode tool to display equivalent Java code

• Find slow-running function and identify cause from java code

Loading an application with large initialization data can result in slow startup times of the application. This can be mitigated by delaying the loading of the list until required. Find a solution whereby the data can be loaded on demand.

• Manually implement a lazy initialization pattern with a backing property

• Replace the pattern with the Kotlin lazy delegate

• Run code and check that both results are the same

When passing a lambda to a higher order function as an argument, extra methods can be generated and boxing and unboxing can occur, resulting in additional performance overheads. Find a solution which removes the additional methods and any boxing/unboxing that may occur when passing a lambda as a function argument.

• Create a capturing lambda expression which creates extra methods in Java

• Create a lambda that implements boxing and unboxing in Java

• Inline functions and verify the removal of methods, boxing, and unboxing in Java

Creating public properties in a companion object will result in additional getter and setter methods being created. This can make an additional performance overhead. Find a solution which removes the creation of the extra setter and getter methods.

• Add a const keyword to public property

• Add a @JvmField annotation to the public property

• View equivalent Java code to confirm the removal of methods

Running multiple operations, such as chaining filter and map calls on large collections, can result in poor performance. Find a solution to improve performance when running multiple operations on large collections.

• Use Kotlin Bytecode tool to identify performance issues

• Replace the implementation with a sequence

• View equivalent Java code to confirm the removal of temporary lists

When calling Android APIs using Kotlin, additional boilerplate code is required for some simple method calls. The Android Toast function, for example, requires an additional sub-method, context, time duration, and then an apply call. The solution will be to replace Android Toast with the KTX core toast method.

• Highlight the issue by demonstrating the Android Toast call

• Replace Android Toast with KTX core toast

• Run KTX core toast to verify the same output

When making SQLite transactions, a number of calls need to be made in a try-finally harness to ensure that the SQLite transaction is completed. The harness, along with three SQLite transaction calls, adds a significant amount of boilerplate code and complexity. Replace the Android SQLite transactions with the KTX SQLite module.

• Demonstrate the problem by executing a SQLite transaction

• Replace the Android SQLite transaction with a KTX SQLite transaction

• Execute the KTX SQLite transaction code to verify the output

When replacing Android fragments using the FragmentManager, additional methods such as beginTransaction and commit are required. Yet again, boilerplate code! Replace the Android Fragment transaction code with the KTX fragment transaction.

• Demonstrate the issue by implementing an Android fragment transaction

• Replace the Android transaction with the KTX fragment transaction

• Run code to verify that the operation completes the same

Creating certain types of collections such as ArraySet will involve code to manually create a value and then populate the items in the array one at a time, before returning the populated ArraySet. Use the KTX collection module to create an ArraySet with a single method call.

• Demonstrate the issue by implementing an ArraySet the Android way

• Replace the Android code with the KTX collection arraySetOf method

• Run code to verify that the same ArraySet collection is created

When implementing background tasks, the device API level and capabilities will have to be checked before deciding on a solution, which could be JobScheduler, Firebase JobDispatcher, or AlarmManager. The WorkManager will do the API and capability check, along with selecting the correct background implementation.

• Implement a worker to populate a collection in a background task

• Implement a worker that provides notification updates from the background task

• Send data and observe updates from the workers

In this video, we will see what are the language features and how does it look like compared to Java.

• Who stands behind the language, what are the features

• First look at the language syntax

• Compared to Java, language is more concise and less verbose

This video explains what are the language features, how does it look like compared to Java.

• Explore Kotlin compiler targets

• Execute on the JVM

• Use Java build tools for compilation

What can you build with Kotlin?

• Use of Kotlin in Android apps

• Use of Kotlin in web apps

• Use of Kotlin in desktop apps

How to setup the IDE?

• Install Kotlin plugin

• Configure Gradle for Kotlin

• Create first Kotlin file

In this video, we will see what the properties in Kotlin are and learn how they are different from Java.

• Explore keywords for declaring properties

• Learn to declare a read only property, and a mutable property

• Understand how to call and initialize properties from Kotlin and Java

What are the functions and function variables in Kotlin?

• Learn to declare a function and explore keywords for declaring variables

• Explore default visibility modifiers and study the read only and mutable variables

• Understand the use of functions in Kotlin and use variables inside the functions

What are default function arguments?

• Learn default functions arguments

• Annotate functions to be used from Java

• Explore calling functions with default arguments

What are named function arguments?

• Learn to define named function arguments

• Understand how to call them in Kotlin

• Explore calling functions with named arguments

What are Control flow structures in Kotlin and how are they different from Java?

• Explore If and When statements in Kotlin

• Study Do/While loops and For loops

• Learn to handle exceptions with try/catch/finally

What are classes and constructors?

• Learn to declare a class

• Declare primary and secondary constructor

• Initialize classes

In this video, we will see which visibility modifiers are available.

• Explore Kotlin’s visibility modifiers

• Learn the differences between Kotlin and Java

• Declare inner classes

What are the Interfaces in Kotlin?

• Explore interface declaration

• Implement the interfaces

• Learn the overriding methods

In this video, we will learn what is object Oriented programming in Kotlin and extending classes.

• Explore extending classes

• Declare abstract classes

• Explore the overriding methods

What is Kotlin’s null safety?

• Achieve null safety in Kotlin

• Explore operators for dealing with null able types

• Understand smart casting

What are compiler generated methods?

• Define data classes

• Explore hashCode, equals and toString methods generation

• Understand equals and reference equals checks

What is object keyword in Kotlin?

• Learn to create singletons

• Create companion objects

• Create anonymous inner classes

What are lambdas and how they improve the readability of the code?

• Explore the code without lambdas and its verbosity

• Learn about lambda syntax

• Defining lambdas

What are the Function types in Kotlin?

• Declaring a function type

• Invoking function types

• Explore member references

What are the useful functions from the standard library API?

• Explore the collection extension functions

• Learn about functional like programing with collections extension functions

• Explore other useful functions

What is the functionality in existing types?

• Explore extension functions syntax

• Calling extension functions

• Calling extension functions from Java

How to invoke lambdas on a “Receiver” object?

• Learn about receiver functions syntax

• Invoking receiver functions

• Explore receiver functions from standard library

What are inline functions and how do they reduce the overhead of lambdas?

• Explore inline functions syntax

• See how in lining works

• Learn about in lining restrictions

What are Generics in Kotlin?

• Understand the basics of Generics

• Explore Classes and methods with generic type parameters

• Putting constraints to generic types

How to avoid Type erasure limitations?

• Explore type erasure

• Access generic parameter at runtime with reified generics

• Implement reified generics

What is operator overloading in Kotlin?

• Understand the functioning of operator overloading in Kotlin

• Explore syntax for operator overloading

• Learn from the examples of overloaded operators with collections

What are delegated properties and what are their benefits?

• Reusing code with delegated properties

• Explore delegated properties requirements and syntax

• Implement delegated properties with Kotlin compiler

What are the differences between Java and Kotlin type system?

• Understand the Kotlin base type

• Explore List and map interfaces in Kotlin

• Use reflection on Kotlin types

In this video, we will understand the options provided by Kotlin for concurrent programming.

• Ensuring thread safety

• Kotlin uses functions and annotations

• Using Java concurrent constructs in Kotlin

The aim of this video is to explain coroutines.

• Problems with current state of asynchronous programming

• Coroutines are suspend able functions

• How compiler compiles coroutines

In this video, we will use library functions to start coroutines.

• Explore what is needed to execute suspend able function

• Using library functions launch and async

• Creating a coroutine from a API that uses callbacks

This video will help you learn from the examples of Coroutine usage in Android.

• Adding coroutines to Android Studio project

• Using Android coroutine context to launch a coroutine

• Exception handling and coroutine cancellation

In this video, we will understand what domain specific languages are.

• DSL’s specialize in specific domains

• Internal and external DSL’s

• Learn from the example of HTML building DSL with Kotlin

The aim of this video is to explain Kotlin features that make building DSLs easy.

• Learn about the receiver functions

• Explore the extension functions

• Understand the infix methods

In this video, you will learn how to use Kotlin to build a validation DSL.

• Explaining classes needed for this DSL

• Using receiver, extension and infix function

• Syntax of validation DSL