Kotlin Code

Intro 

At Google I/O 2019, we announced that Android development will be increasingly Kotlin-first, and we’ve stood by that commitment. Kotlin is an expressive and concise programming language that reduces common code errors and easily integrates into existing apps. If you’re looking to build an Android app, we recommend starting with Kotlin to take advantage of its best-in-class features.In an effort to support Android development using Kotlin, we co-founded the Kotlin Foundation and have ongoing investments in improving compiler performance and build speed. To learn more about Android's commitment to being Kotlin-first, see Android's commitment to Kotlin .Are you a beginner looking to learn Kotlin coding? Then you have come to the right place! In this blog post, we will be sharing our top 10 tips for mastering the basics of Kotlin coding. Whether you're just starting out or have a few projects under your belt, you can use these tips to taketake your coding skills to the next level. We'll be discussing everything from getting started to debugging and everything in between, so read on and get ready to become a Kotlin coding master

Why is Android development Kotlin-first?

We reviewed feedback that came directly from developers at conferences, our Customer Advisory Board (CAB), Google Developers Experts (GDE), and through our developer research. Many developers already enjoy using Kotlin, and the request for more Kotlin support was clear. Here’s what developers appreciate about writing in Kotlin:You can do more with less. Express your ideas and reduce the amount of boilerplate code. 67% of professional developers who use Kotlin say Kotlin has increased their productivity.Safer code: Kotlin has many language features to help you avoid common programming mistakes such as null pointer exceptions. Android apps that contain Kotlin code are 20% less likely to crash.

Interoperable:  

Call Java-based code from Kotlin, or call Kotlin from Java-based code. Kotlin is 100% interoperable with the Java programming language, so you can have as little or as much of Kotlin in your project as you want.

Structured Concurrency: Kotlin coroutines make asynchronous code as easy to work with as blocking code. Coroutines dramatically simplify background task management for everything from network calls to accessing local data.

What does Kotlin-first mean?

When building new Android development tools and content, such as Jetpack libraries, samples, documentation, and training content, we will design them with Kotlin users in mind while continuing to provide support for using our APIs from the Java programming language.

1) Get started with a basic Hello, World! program

Kotlin is a powerful and versatile programming language, and the perfect starting point for those new to coding. Writing your first "Hello, World!" program is a great way to get a feel for the language and its syntax.To get started, you will need to create a project in your preferred Integrated Development Environment (IDE). Once your project is ready, open the main.kt file in the project's src folder. In the file, type the following code: fun main() { 

The code above prints the text “Hello, World!” when you run it. The keyword fun is used to declare a function; main() is the name of the function. The line println("Hello, World!") is responsible for printing the text. Once you have written the code, press the Run button to execute the program. You should see “Hello, World!” printed in the console. Congratulations! You have just written your first program in Kotlin.

2) Declare immutable variables using the val keyword

The val keyword is used in Kotlin to declare immutable variables. An immutable variable is a variable that cannot be modified after it has been assigned a value. This helps to ensure that your code will not inadvertently change the value of an immutable variable. When declaring an immutable variable, you must specify the type of the variable. This can be done using type inference or by explicitly declaring the type. Here is an example of an immutable variable declaration using type inference: val name = "Bob" // name is a StringAnd here is an example of an immutable variable declaration with an explicit type: val age: Int = 25 // age is an IntegerOnce a value has been assigned to an immutable variable, it cannot be changed. This makes your code more predictable and easier to debug. Additionally, when declaring functions and classes, the val keyword is used to denote parameters that cannot be changed within the body of the function or class. When writing code in Kotlin, the val keyword should always be used when declaring immutable variables. This will help make your code more readable, maintainable, and secure.

3) Use explicit types when needed

Using explicit types when coding with Kotlin is an important part of writing code that is both easy to read and understand. Explicit types tell the compiler exactly what type of data is expected in a given variable, helping to ensure the correctness of the code. They also help to make code more understandable for other developers who may be reading your code. When declaring variables, it’s best practice to include the type explicitly so that readers of your code are aware of what type is expected for that variable. For example, if you’re expecting a String to be stored in a variable, use the type String instead of just var or val. This helps to clarify what type should be stored in the variable and ensures that the compiler won’t try to put any other type into the variable.In addition to explicitly declaring the type when declaring variables, you can also explicitly declare the type when calling functions. This makes it easier for other developers to see what types are being passed into and returned from the function. It also makes it easier for the compiler to detect any potential errors related to the function’s parameters or return types. By using explicit types when needed, you can create code that is both easy to read and understand and ensures that your code will compile without any unexpected errors.

4) Learn the basics of object-oriented programming in Kotlin

Object-oriented programming (OOP) is a way of organizing and designing software applications by creating objects and classes. In Kotlin, the basic building blocks of OOP are classes, which are collections of related data and functions. Classes can be used to represent real-world entities like people, cars, or animals. Kotlin has several features that make object-oriented programming easier, including encapsulation, inheritance, and polymorphism. Encapsulation allows you to group related data and functions into a single unit called a class. Inheritance allows classes to share behavior and properties with each other. Polymorphism allows code to use a common interface for different types of objects. Kotlin also supports interfaces, abstract classes, and generics. Interfaces allow classes to declare the methods they must implement without having to provide an implementation. Abstract classes provide partial implementations of their members and require subclasses to provide the rest. Generics allow you to write code that works with multiple types without having to write separate implementations for each type. By learning the basics of object-oriented programming in Kotlin, you can write code that is easier to read, maintain, and extend. You will be able to create sophisticated applications that take advantage of all the features that Kotlin has to offer.

5) Take advantage of Kotlin's null safety features

Kotlin provides an incredibly robust set of null safety features. These features are designed to help you reduce the likelihood of a NullPointerException, as well as make your code more reliable and easier to read.To start, Kotlin does not allow you to assign or return null in any variable unless it has been explicitly declared with the “nullable” modifier. This ensures that any variable which is not marked as nullable will never be null, which eliminates a whole class of bugs.Kotlin also allows you to safely access properties on an object, even if the object is null. If you attempt to access a property on a null object, Kotlin will automatically return a default value instead of throwing an exception. You can also use the “?” operator to denote that you’d like to perform an action only if an object is non-null.Finally, Kotlin allows you to chain multiple calls on an object, with each call only being executed if the previous call does not return null. This is known as safe-calls and it can help you write more concise code and avoid additional checks for null values.By taking advantage of all of these features, you can drastically reduce the likelihood of encountering a dreaded NullPointerException while developing with Kotlin.

8) Use lambdas to write concise code

Lambdas are a great way to write concise code in Kotlin. A lambda is an anonymous function that can be used anywhere a regular function can be used. It consists of a parameter list, an arrow (->) and a body. Lambdas make it easy to pass functions as parameters and make it easier to manipulate collections of data.

For example, you can use a lambda to sort a list of integers: 

val numbers = listOf(1,2,3,4,5) 

numbers.sortBy { it * -1 } 

// This will sort the list in descending order 

You can also use lambdas to filter a collection: 

val numbers = listOf(1,2,3,4,5) 

numbers.filter { it % 2 == 0 } // This will return a list of all even numbers 

Using lambdas allows you to express complex operations in just a few lines of code. They are a powerful tool for writing concise and readable code and are essential for working with Kotlin.