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Kotlin Programming Cookbook
Kotlin Programming Cookbook

Kotlin Programming Cookbook: Explore more than 100 recipes that show how to build robust mobile and web applications with Kotlin, Spring Boot, and Android

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Profile Icon Aanand Shekhar Roy Profile Icon Rashi Karanpuria
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€41.99
Full star icon Full star icon Full star icon Half star icon Empty star icon 3.3 (3 Ratings)
Paperback Jan 2018 434 pages 1st Edition
eBook
€22.99 €32.99
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€41.99
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Arrow left icon
Profile Icon Aanand Shekhar Roy Profile Icon Rashi Karanpuria
Arrow right icon
€41.99
Full star icon Full star icon Full star icon Half star icon Empty star icon 3.3 (3 Ratings)
Paperback Jan 2018 434 pages 1st Edition
eBook
€22.99 €32.99
Paperback
€41.99
Subscription
Free Trial
Renews at €18.99p/m
eBook
€22.99 €32.99
Paperback
€41.99
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Renews at €18.99p/m

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Kotlin Programming Cookbook

Control Flow

The following recipes will be covered in this chapter:

  • Assigning result to an expression using the if keyword
  • Using range with the when expression
  • Using when with custom objects
  • Using trycatch as an expression
  • How to write a swap function in Kotlin using the also function
  • How to throw a custom exception in Kotlin
  • How to make a multiconditional loop in Kotlin

Introduction

Control flows are the basic building block of every programming language. What's different in Kotlin is that you can use a few of those control flows as an expression, such as try-catch, if-else, when, and so on. In this chapter, we will go through some of the control flows offered by Kotlin and learn to use them. Furthermore, we will also see how they provide much more power than Java control flows. So let's get started!

Assigning result to an expression using the if keyword

In Kotlin if is special because it returns values. That is why we can use an if statement to assign values to a result. This removes the need for a ternary operator in Kotlin. Let's see how we can use if statements to assign value.

Getting ready

You need to install a preferred development environment that compiles and runs Kotlin. You can also use the command line for this purpose, for which you need Kotlin compiler installed, along with JDK. I am using the command line for compiling and running my Kotlin code for this recipe.

How to do it...

...

Using range with the when expression

In Kotlin, when is like a super-powered switch control statement. However, that's not all it can do. There's a lot of amazing logic that you can build with the when statement, one example of which is using a range with the when statement. We will take a look at that in this recipe.

Getting ready

You need to install a preferred development environment that compiles and runs Kotlin. You can also use the command line for this purpose, for which you need Kotlin compiler installed, along with JDK. I am using the command line to compile and run my Kotlin code for this recipe.

...

Using when with custom objects

In Kotlin, when is already so powerful but did you know you can also use custom objects in when? Amazing, right? Let's go about implementing it.

Getting ready

You need to install a preferred development environment that compiles and runs Kotlin. You can also use the command line for this purpose, for which you need Kotlin compiler installed, along with JDK. I am using the command line to compile and run my Kotlin code for this recipe.

How to do it...

Create a file and name it whenWithObject.kt, and then, let's try when with a custom...

Using try–catch as an expression

Exceptions in Kotlin are both similar and different compared to those in Java. In Kotlin, Throwable is the superclass of all the exceptions, and every exception has a stack trace, message, and an optional cause.

The structure of trycatch is also similar to that used in Java. In Kotlin, here's how a trycatch statement looks:

try {
// some code to execute
}
catch (e: SomeException) {
// exception handler
}
finally {
// optional finally block
}

At least one catch block is mandatory and the finally block is optional, and so it can be omitted.

In Kotlin, trycatch is special as it enables it to be used as an expression. In this article, we will see how we can use trycatch as an expression.

Getting ready...

How to write a swap function in Kotlin using the also function

Swapping two numbers is one of the most common things you do in programming. Most of the approaches are quite similar in nature: Either you do it using a third variable or using pointers.

In Java, we don't have pointers, so mostly we rely on a third variable.

You can obviously use something as mentioned here, which is just the Kotlin version of Java code:

var a = 1
var b = 2
run { val temp = a; a = b; b = temp }
println(a) // print 2
println(b) // print 1

However, in Kotlin, there is a very quick and intuitive way of doing it. Let's see how!

Getting ready

You need to install a preferred development environment that compiles and runs Kotlin. You can also use...

How to throw a custom exception in Kotlin

Sometimes, there are cases where you want to create your own exception. If you are creating your own exception, it's known as a custom exception or user-defined exception.

These are used to customize the exception according to a specific need, and using this, you can have your own exception and a message. In this recipe, we will see how to create and throw a custom exception in Kotlin.

Getting ready

You need to install a preferred development environment that compiles and runs Kotlin. You can also use the command line for this purpose, for which you need Kotlin compiler installed, along with JDK. I am using IntelliJ IDE to compile and run my Kotlin code for this recipe.

...

How to make a multiconditional loop in Kotlin

Conditional loops are common to any programming language you pick. If you apply multiple conditions on a loop, it is called a multiconditional loop. A simple example of a multiconditional loop in Java is illustrated here:

int[] data = {5,6,7,1,3,4,5,7,12,13};
for(int i=0;i<10&&i<data[i];i++){
System.out.println(data[i]);
}

The preceding code on execution will print out 5, 6, and 7. Let's see how we can use a multiconditional loop in Kotlin. We will be looking at a functional approach to the same thing in Kotlin.

Getting ready

You need to install a preferred development environment that compiles and runs Kotlin. You can also use the command line for this purpose...

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Key benefits

  • Practical solutions to your common programming problems with Kotlin 1.1
  • Leverage the functional power of Kotlin to ease your Android application development
  • Learn to use Java code in conjunction with Kotlin

Description

The Android team has announced first-class support for Kotlin 1.1. This acts as an added boost to the language and more and more developers are now looking at Kotlin for their application development. This recipe-based book will be your guide to learning the Kotlin programming language. The recipes in this book build from simple language concepts to more complex applications of the language. After the fundamentals of the language, you will learn how to apply the object-oriented programming features of Kotlin 1.1. Programming with Lambdas will show you how to use the functional power of Kotlin. This book has recipes that will get you started with Android programming with Kotlin 1.1, providing quick solutions to common problems encountered during Android app development. You will also be taken through recipes that will teach you microservice and concurrent programming with Kotlin. Going forward, you will learn to test and secure your applications with Kotlin. Finally, this book supplies recipes that will help you migrate your Java code to Kotlin and will help ensure that it's interoperable with Java.

Who is this book for?

This book will appeal to Kotlin developers keen to find solutions for their common programming problems. Java programming knowledge would be an added advantage.

What you will learn

  • Understand the basics and object-oriented concepts of Kotlin Programming
  • Explore the full potential of collection frameworks in Kotlin
  • Work with SQLite databases in Android, make network calls, and fetch data over a network
  • Use Kotlin s Anko library for efficient and quick Android development
  • Uncover some of the best features of Kotlin: Lambdas and Delegates
  • Set up web service development environments, write servlets, and build RESTful services with Kotlin
  • Learn how to write unit tests, integration tests, and instrumentation/acceptance tests.
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Length: 434 pages
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Table of Contents

15 Chapters
Installation and Working with Environment Chevron down icon Chevron up icon
Control Flow Chevron down icon Chevron up icon
Classes and Objects Chevron down icon Chevron up icon
Functions Chevron down icon Chevron up icon
Object-Oriented Programming Chevron down icon Chevron up icon
Collections Framework Chevron down icon Chevron up icon
Handling File Operations in Kotlin Chevron down icon Chevron up icon
Anko Commons and Extension Function Chevron down icon Chevron up icon
Anko Layouts Chevron down icon Chevron up icon
Databases and Dependency Injection Chevron down icon Chevron up icon
Networking and Concurrency Chevron down icon Chevron up icon
Lambdas and Delegates Chevron down icon Chevron up icon
Testing Chevron down icon Chevron up icon
Web Services with Kotlin Chevron down icon Chevron up icon
Other Books You May Enjoy Chevron down icon Chevron up icon

Customer reviews

Rating distribution
Full star icon Full star icon Full star icon Half star icon Empty star icon 3.3
(3 Ratings)
5 star 33.3%
4 star 33.3%
3 star 0%
2 star 0%
1 star 33.3%
Luis Espinoza Feb 23, 2018
Full star icon Full star icon Full star icon Full star icon Full star icon 5
It's a great book, it contains a lot of recipes that will help you on your journey as a kotlin developer.
Amazon Verified review Amazon
Amazon Customer Mar 12, 2018
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
I like the variety of recipes, touching all the parts of the Kotlin language, including Anko. What I miss in the book is a little deeper explanation of why things and recipes should be done the way they're done.
Amazon Verified review Amazon
Amazon Customer Oct 12, 2018
Full star icon Empty star icon Empty star icon Empty star icon Empty star icon 1
Book does stand-up to the Mark, what it talks about.It doesn't provide proper information about Kotlin language syntax, Data Types, String, Collection & their uses.In Middle pages contents are not at all proper. Contents are single line vertically running content.Is there any way for Re-Fund for e-books.
Amazon Verified review Amazon
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