What is the difference between “var” and “val” in Kotlin?

If you want to develop Android apps or multi-platform applications with the JVM, you can do it quicker and simpler with Kotlin than with Java. Jemerov wanted a language that had all the features of more modern programming languages, would run on the JVM, and would compile as fast as Java. So, these are some of the features that add to the popularity of Kotlin programming language. Now let’s take a look at the various platforms on which you write and develop your Kotlin applications. Kotlin is often considered easier due to its concise syntax, modern features, and seamless interoperability with Java.

But, Kotlin made inroads into server-side web development since it was so much easier for developers to work with. Having a mobile presence is a requirement for most businesses since most people access the internet now through mobile phones. Android accounts for over 70% of the market share of mobile phones, so even if Kotlin was only for Android development, Kotlin developers would be in high demand. Kotlin allows local functions to be declared inside of other functions or methods. By placing the preceding code in the top-level of a package, the String class is extended to include a lastChar function that was not included in the original definition of the String class. Kotlin 1.3 added support for contracts,[35] which are stable for the standard library declarations, but still experimental for user-defined declarations.

What Is Kotlin Used For?

You can use a non-nullable type with impunity, but you have to test a nullable type for null values before using it. If you need to allow nulls, for example to hold SQL query results, you can declare a nullable type by appending a question mark to the type, e.g. For Groovy fans, Kotlin implements builders; in fact, Kotlin builders can be type checked. Kotlin supports delegated properties, which can be used to implement lazy properties, observable properties, vetoable properties, and mapped properties.

Kotlin compiles to the same byte code as Java, interoperates with Java classes in natural ways, and shares its tooling with Java. Because there is no overhead for calling back and forth between Kotlin and Java, adding Kotlin incrementally to an Android app currently in Java makes perfect sense. The few cases where the interoperability between Kotlin and Java code lacks grace, such as Java set-only properties, are rarely encountered and easily fixed. To override a superclass method, the method itself must be marked open, and the subclass method must be marked override.

Android Widgets: Custom Spinner in Android

Kotlin silently and reliably infers what is called a “platform type” that behaves exactly like a Java type, meaning that is nullable but can generate null-pointer exceptions. Kotlin may also inject an assertion into the code at compile time to avoid triggering an actual null pointer exception. There’s no explicit language notation for a platform type, but in the event Kotlin has to report a platform type, such as in an error message, it appends ! Allowing top-level functions is just the beginning of the functional programming story for Kotlin. The language also supports higher-order functions, anonymous functions, lambdas, inline functions, closures, tail recursion, and generics.

• Kotlin is a modern but already mature programming language designed to make developers happier.
• Pinterest was the poster child for Android apps written in Kotlin as early as November 2016, and it was mentioned prominently at Google I/O 2017 as part of the Kotlin announcement.
• Yes, it’s possible to write Android applications in Scala, but few developers bother.
• If you look at GitHub (as of October 2022) and search for Android repositories, you’ll find about 50,000 that use Java, 24,000 that use Kotlin, and (ahem) 73 that use Scala.

Instead we use val to declare this as an immutable variable. As an immutable variable a HashMap cannot become anything rather than a HashMap, but it can be used as usual to store key value pairs. Kotlin is supported as a first-class language on Android. There are hundreds of applications already using Kotlin for Android, such as Basecamp, Pinterest and more. For more information, check out the resource on Android development. Kotlin is 100% interoperable with the Java programming language and major emphasis has been placed on making sure that your existing codebase can interact properly with Kotlin.

Features of Kotlin

It has become very popular since it is compatible with Java (one of the most popular programming languages out there), which means that Java code (and libraries) can be

used in Kotlin programs. Kotlin supports the specification of a “primary constructor” as part of the class definition itself, consisting of an argument list following the class name. Additionally, when defining a subclass, properties in super-interfaces and super-classes can be overridden in the primary constructor. Kotlin is easier to understand than Java, which makes code easier to read and comprehend.

You can easily call Kotlin code from Java and Java code from Kotlin. There’s also an automated Java-to-Kotlin converter built into the IDE that simplifies migration of existing code. Speaking of avoiding common errors, Kotlin was designed to eliminate the danger of null pointer references and streamline the handling of null values. It does this by making a null illegal for standard types, adding nullable types, and implementing shortcut notations to handle tests for null.

In addition, there are specific frameworks written in Kotlin such as Ktor. For more information, check out the resource on server-side development. An Android developer might choose Java over Kotlin if they are new to Android software development. Historically, most examples of Android documentation are in Java.

A new developer combing through these might find it easier to engage with them in Java rather than converting to Kotlin. Kotlin has great support and many contributors in its fast-growing global community. Enjoy the benefits of a rich ecosystem with a wide range of community libraries. Help is never far away — consult extensive community resources or ask the Kotlin team directly.

Contracts are inspired by Eiffel’s design by contract[36] programming paradigm. The website has a bunch of online resources, including Kotlin Digests by community members, a newsletter, https://www.globalcloudteam.com/ a podcast and more. Kotlin developers hang out on the Kotlin forums, StackOverflow and more actively on the Kotlin Slack (with close to members as of April 2020).

Kotlin is sponsored by JetBrains and Google, through the Kotlin Foundation. Other programming languages can be dynamically typed, where the compiler assigns a type to all the variables at runtime. A good example of a dynamically typed programming language is Python. In Python, programmers can write code faster because they don’t need to specify variable types every time the code runs, which translates into less verbose code. JavaScript is also a dynamically typed language so when we declare a variable we don’t need to specify its type. Kotlin and Java are both general-purpose, statically typed programming languages.

Kotlin originated at JetBrains, the company behind IntelliJ IDEA, in 2010, and has been open source since 2012. The Kotlin project on GitHub has more than 770 contributors; while the majority of the team works at JetBrains, there have been nearly 100 external contributors to the Kotlin project. JetBrains uses Kotlin in many of its products including its flagship IntelliJ IDEA. A lot of back-end web development is done in Java, using frameworks like Spring.

Null pointer exceptions are one of the most prevalent problems in Java projects. NullPointerException is an error generated in Java when the code tries to access an object with a null reference. To solve this in Java, programmers use preventive techniques like doing null checks before referencing an object’s methods or properties. Developers can end up doing null checks all over their code without actually understanding the possible states of an object. Using val in our code makes it easier to read and incredibly compact. Using the example above, we can see how we don’t need to declare the variable type in the beginning of a HashMap.

Pinterest was the poster child for Android apps written in Kotlin as early as November 2016, and it was mentioned prominently at Google I/O 2017 as part of the Kotlin announcement. In addition, the Kotlin team likes to cite the Evernote, Trello, Gradle, Corda, Spring, and Coursera apps for Android. To avoid the verbose grammar normally needed for null testing, Kotlin introduces a safe call, written ? Many asynchronous mechanisms available in other languages can be implemented as libraries using Kotlin coroutines.