Here, 5 is assigned to variable age using =operator. to the Objective-C/Swift interop. It checks whether the left-hand side expression is reference equal to null, and, if it is, evaluates and return the right-hand side expression. The Elvis operator(? Kotlin mainly targets the JVM, but also compiles to JavaScript (e.g. We can use it to check if any variable is null or not and it allows us to use one default value if the value is null. Mi Választ Minden Kérdésre. // - or if foo() and bar() are non-null, but baz() returns null. [44], In 2020, JetBrains found in a survey of developers who use Kotlin that 56% were using Kotlin for mobile apps, while 47% were using it for a web back-end. This is in contrast to most object-oriented languages such as Java where classes are open by default. However, using if and when expressions help to fill this gap. Similar to C#, Kotlin allows a user to add functions to any class without the formalities of creating a derived class with new functions. Sharad Jaiswal; 22nd Dec, 2019; 472 Followers; Follow ; Submit a Question ; Updated ON. : run { // execute this block if null } But this seems not to be quite as readable as a simple if–else statement. As in C, C++, C#, Java, and Go, the entry point to a Kotlin program is a function named "main", which may be passed an array containing any command-line arguments. I’m sure most of us do think they are equivalent. We have already used simple assignment operator =before. Please help, // Overloading '+' operator using an extension function, "Can't save user ${user.id}: empty $fieldName", // open on the class means this class will allow derived classes, // polymorphic behavior disabled if function overridden in derived class, // polymorphic behavior allowed if function is overridden in derived class, // Explicit use of override keyword required to override a function in derived class, // No need for the open keyword here, it’s already open by default, // This virtual function is already open by default as well, // Class is visible only to current module, // method is only visible to current class, // method is visible to current class and derived classes, // Example of class using primary constructor syntax, // (Only one constructor required for this class), // Example of class using secondary constructor syntax, // (more than one constructor required for this class), // create a data class object like any other class object, // output: Book(name=Kotlin Programming, price=250), // data class with parameters and their optional default values. // Infix functions, extensions, type inference, nullable types, // lambda expressions, labeled this, Elvis operator (? 22. Kotlin is a new generation language and very null safe. But it can lead to some hidden pitfalls if you are not aware of how it works. The Expressivity of Kotlin’s Elvis Operator. The Elvis operator is a terse structure that is present in Kotlin. [40] As of 2020, Kotlin is still most widely used on Android, with Google estimating that 70% of the top 1000 apps on the Play Store are written in Kotlin. Abstract classes define abstract or "pure virtual" placeholder functions that will be defined in a derived class. Author. Safe Calls & the Elvis Operator. Static objects and functions can be defined at the top level of the package without needing a redundant class level. = name?.length // Elvis operator ? Non-Null Assertions. What you'll need. The Importance of Lambdas. You can use the elvis operator and evaluate another block of code with run { ... }: data?.let { // execute this block if not null } ? This might not what you expect when thinking of it as an if/else. PS: Check out the decompiled code of the example above: https://dev.to/vlazdra/a-decompiled-story-of-kotlin-let-and-run-4k83, PPS: Special thanks to Lucas Nobile and Artur Latoszewski for additional inputs here, love the wisdom of the crowd , data?.let{ updateData(data) } ? Many Android apps, such as Google's Home, are in the process of being migrated to Kotlin, and so use both Kotlin and Java. In Java this would be the equivalent of a NullPointerException or NPE for short.Kotlin's type system is aimed to eliminate NullPointerException's from our code. : run { showLoadingSpinner() }, https://twitter.com/vlazdra/status/1287366531987406848?s=20, https://dev.to/vlazdra/a-decompiled-story-of-kotlin-let-and-run-4k83, All-inclusive Vue.js beginner tutorial — building a converter app, How to write production ready Node.js Rest API — Javascript version. Kotlin provides the following keywords to restrict visibility for top-level declaration, such as classes, and for class members: public, internal, protected, and private. 2. if and when Expressions. However, he cited the slow compilation time of Scala as a deficiency. : 0) First, you added the safe call operator to listFiles(). : 0 // The Elvis operator can also execute statements in the case of … Question 11) What are kotlin coroutines? ", "Kotlin for JavaScript - Kotlin Programming Language", "Kotlin for cross-platform mobile development", "Kotlin Foundation - Kotlin Programming Language", "Kotlin is now Google's preferred language for Android app development", "What's New in Kotlin 1.4 - Kotlin Programming Language", "So why did they decide to call it Java? *A better idea: “Actually I’m fine with that code style, though, there’s a better way to unwrap a nullable variable.” Mitigation: Elvis operator is more expressive than we thought. Returning a value from a Kotlin Function 05:20. It is a variant of the ternary operator but for null-safety checking. In February 2012, JetBrains open sourced the project under the Apache 2 license. dispatched based on the runtime type of the object they are called on. Kotlin's type system is aimed at eliminating the danger of null references from code, also known as the The Billion Dollar Mistake.One of the most common pitfalls in many programming languages, including Java, is that accessing a member of a null reference will result in a null reference exception. Kotlin variable declarations and parameter lists have the data type come after the variable name (and with a colon separator), similar to BASIC, Pascal and TypeScript. A full-stack demo has been made with the new Kotlin/JS Gradle Plugin.[19][20]. In Kotlin, to derive a new class from a base class type, the base class needs to be explicitly marked as "open". (This is optional since Kotlin 1.3[28]). [25] Remember, let is returning the result from your block (as does run). An elvis operator expression is a binary expression which uses an elvis operator (?:). [16], Kotlin v1.2 was released on 28 November 2017. Kotlin has become one of the most popular JVM languages in the past few months. for native iOS apps sharing business logic with Android apps. Featuring: syntax highlighting, basic indentation, Syntastic support", "Google makes Kotlin a first-class language for writing Android apps", "Kotlin programming language: How Google is using it to squash the code bugs that cause most crashes", "Introducing Kotlin support in Spring Framework 5.0", "Review of Microservices Frameworks: A Look at Spring Boot Alternatives", "Kotlin Programming - The State of Developer Ecosystem 2020", "Kotlin wins Breakout Project of the Year award at OSCON '19", "KotlinConf 2019: Kotlin Runs Taxes in Norway by Jarle Hansen & Anders Mikkelsen", "Using Kotlin for backend development at Flux", "Groovy and Kotlin Interop at Rocket Travel", "KotlinConf 2019: Kotlin in Space by Maxim Mazin", "KotlinConf 2017 - Frontend Kotlin from the Trenches by Gaetan Zoritchak", "Java/Kotlin Developer - Barclays - Prague - Wizbii", "Kotlin in Production – What works, Whats broken", "How we made Basecamp 3's Android app 100% Kotlin – Signal v. Noise", "Droidcon NYC 2016 - Kotlin in Production", "Kotlin 1.1 Released with JavaScript Support, Coroutines and more", https://en.wikipedia.org/w/index.php?title=Kotlin_(programming_language)&oldid=1000844013, Short description is different from Wikidata, Creative Commons Attribution-ShareAlike License, Integration with common Java build tools is supported including, Corda, a distributed ledger developed by a consortium of well-known banks (such as. You should already be familiar with Java. But what if I told you, it’s not?The if/else is totally binary, it’s either-or. The Elvis operator says, “Use formatString‘s value unless it is null, then use "yyyy/DD/dd".” This line of code delegates to the rigid (non-nullable) function to format the LocalDate. In this lesson, you'll learn what the Kotlin init block is in a class and how you can use it. The right-hand side expression is evaluated only if … In other words, if left expression is not null then elvis operator returns it, otherwise it returns the right expression. Stay aware! It's just easier to read a plain if-else than other Kotlin solutions, such as this solution using the elvis operator. : (null coalescing operator) often referred to as the Elvis operator: The data keyword is used before the class keyword to define a data class.[29]. [15] This is considered to be the first officially stable release and JetBrains has committed to long-term backwards compatibility starting with this version. Additionally, when defining a subclass, properties in super-interfaces and super-classes can be overridden in the primary constructor. Kotlin is being developed by JetBrains, who are responsible for the most famous IDEs out there, most notably IntelliJ IDEA. 21. Manipulating Lists. Class member functions are virtual, i.e. of Questions. It is fancily called the null-coalescing operator. Introduction to Generics. Elvis operator; Destructuring; Properties and backing properties; Default arguments and named parameters; Working with collections; Extension functions ; Top-level functions and parameters; let, apply, with, and run keywords; Assumptions. Kotlin 1.3 adds (experimental) support for contracts[26] (inspired by Eiffel's design by contract[27] programming paradigm). [41], In addition to its prominent use on Android, Kotlin is gaining traction in server-side development. Remember, we can chain them: if we now add the Elvis operator here, it will get executed depending on the expression to its left side: so if any expression in there is null, the Elvis block will get called. [21], Development lead Andrey Breslav has said that Kotlin is designed to be an industrial-strength object-oriented language, and a "better language" than Java, but still be fully interoperable with Java code, allowing companies to make a gradual migration from Java to Kotlin. This article contains quotations from Kotlin tutorials which are released under an Apache 2.0 license. 22nd Dec, 2019. (safe navigation operator) can be used to safely access a method or property of a possibly null object. Pada artikel sebelumnya, penulis telah membahas mengenai setup project kotlin dengan menggunakan gradle.Nah pada artikel ini, penulis akan membahas sedikit mengenai null safety pada kotlin. Kotlin Elvis Operator(? In this tutorial, we’ll look into a few different ways to mimic the ternary operator. [13], JetBrains hopes that the new language will drive IntelliJ IDEA sales.[14]. But let me show you some code: I think most of us love the way we can easily write null safe code with Kotlin like this: And it is super easy to add an alternative case: Do you think the following code is basically the same as the above? 24. Kotlin on Android is seen as beneficial for its null-pointer safety as well as for its features that make for shorter, more readable code. Scripts can be run by passing the -script option and the corresponding script file to the compiler. [22], Semicolons are optional as a statement terminator; in most cases a newline is sufficient for the compiler to deduce that the statement has ended.[23]. Compiling it directly to bytecode helps to achieve faster compile time and makes no difference between Java and Kotlin for JVM. ", "Kotlin 1.0 Released: Pragmatic Language for JVM and Android | Kotlin Blog", "Kotlin 1.2 Released: Sharing Code between Platforms | Kotlin Blog", "Multiplatform Projects - Kotlin Programming Language", "Kotlin/kotlin-full-stack-application-demo", "Kotlin full stack app demo: update all involving versions to work with 1.3.70 release", "JVM Languages Report extended interview with Kotlin creator Andrey Breslav", "What's New in Kotlin 1.3 - Kotlin Programming Language", "Design by Contract (DbC) design considerations", "Kotlin Examples: Learn Kotlin Programming By Example", "Getting Started with Eclipse Neon – Kotlin Programming Language", "JetBrains/kotlin-eclipse: Kotlin Plugin for Eclipse", "Using Maven – Kotlin Programming Language", "Using Ant – Kotlin Programming Language", "Using Gradle – Kotlin Programming Language", "udalov/kotlin-vim: Kotlin plugin for Vim. : Csinál Kotlinban? Mit csinál? Posted In. If the object is null, the method will not be called and the expression evaluates to null.? Perl and Unix shell style string interpolation is supported. It will finish evaluating everything on the left before checking if the operator is needed. a 2D coordinate object might be destructured into two integers x and y. 23. In other words, an extension function is a helper function that has access to all the public interface of a class which it can use to create a new function interface to a target class and this function will appear exactly like a function of the class, appearing as part of code completion inspection of class functions. When Kotlin was announced as an official Android development language at Google I/O in May 2017, it became the third language fully supported for Android, in addition to Java and C++. The Elvis operator in Kotlin is an operator that receives two inputs and returns the first argument if it is non-null or the second one otherwise. Kotlin is designed to interoperate fully with Java, and the JVM version of Kotlin's standard library depends on the Java Class Library,[3] but type inference allows its syntax to be more concise. To understand why we have to look closer to how it works. In addition to the classes and member functions (equivalent to methods) of object-oriented programming, Kotlin also supports procedural programming with the use of functions. Suppose we have a nullable reference a, we can say "if a is not null, use it, otherwise use some non-null value x" var a: String? : that perfectly complements the safe call operator for handling else cases. 9. So if you want the expected behavior, better do something explicitly as: Remember, everything in Kotlin is resolving to some type including every expression. However, in cases where more than one constructor is needed for a class, a more general constructor can be used called secondary constructor syntax which closely resembles the constructor syntax used in most object-oriented languages like C++, C#, and Java. 8) Is there any Ternary Conditional Operator in Kotlin like in Java? Briefly speaking, there is no ternary operator in Kotlin. Kotlin’s when {} Block When {} block is essentially an advanced form of the switch-case statement known from Java. Line 45 of FileHelpers.kt file, listFiles() returns null when file is not a directory. A data class often is written without a body, though it is possible to give a data class any methods or secondary constructors that are valid for any other class. One special reason is that it experienced a lot of attention in the Android community after Google made Kotlin an official language for Android development. Extension Properties. Kotlin provides Data Classes to define classes whose primary purpose is storing data. For compatibility with Java, Kotlin provides a JvmName annotation which specifies a class name used when the package is viewed from a Java project. For example, the Map.Entry object supports destructuring to simplify access to its key and value fields: Kotlin allows local functions to be declared inside of other functions or methods. Read more about the elvis operator in the official documentation. All nullable objects must be declared with a "?" // - or if foo() is non-null, but bar() returns null. At Google I/O 2017, Google announced first-class support for Kotlin on Android. Operations on nullable objects need special care from developers: null-check must be performed before using the value. Sebagai developer java, anda pasti sering menemui yang namanya NullPointerException atau disingkat dengan NPE. It is also used to check the null safety of values. [11], The name comes from Kotlin Island, near St. Petersburg. Kotlin Elvis Operator with introduction, architecture, class, object, inheritance, interface, generics, delegation, functions, mixing java and kotlin, java vs kotlin etc. It takes the following form: (expression) ? (Elvis Operator) 2021; A Csapat Szerzők. Disclaimer: This reference has originally been published as a DZone Refcard. Kotlin Elvis Operator (? ". Most Kotlin users were targeting Android (or otherwise on the JVM), with only 6% using Kotlin Native. Caster.io. [10] One of the stated goals of Kotlin is to compile as quickly as Java. Other than the else that belongs explicit to an if , the Elvis operator is not tied to a single ?. Instead, Kotlin adds the concept of an extension function which allows a function to be "glued" onto the public function list of any class without being formally placed inside of the class. [6], On 7 May 2019, Google announced that the Kotlin programming language is now its preferred language for Android app developers. Kotlin is interoperable with Java because it uses JVM bytecode. How to Create a Function in Kotlin 05:41. ⭐ Kite is a free AI-powered coding assistant that will help you code faster and smarter. [46] It's the fourth most loved programming language according to the 2020 Stack Overflow Developer Survey. Kotlin makes working with Strings easy with String templates. Unlike other languages, if and when in Kotlin are expressions. Q19: When would you use Elvis operator in Kotlin? Abstract classes are open by default. No there is no ternary conditional operator in Kotlin language. Kotlin v1.3 was released on 29 October 2018, bringing coroutines for asynchronous programming. No. Kotlin can also be used as a scripting language. Question 10) What is init block in Kotlin? So this is depending on whatever doSomething() returns! Tutoriel Kotlin: kotlin safety, Elvis operator in kotlin, safe call in Kotlin août 2019 En tant que développeur, l'un des bugs les plus récurant que l'on rencontre dans nos applications c'est NullPointerException. Question 9) What is the Elvis Operator in Kotlin? Kotlin Single Line Expressions 04:08. Kotlin supports the specification of a "primary constructor" as part of the class definition itself, consisting of an argument list following the class name. Kotlin Functions inside of other Functions 03:02. x ? Kotlin streamlines this with the Elvis operator, ?:. But with the Elvis operator, it might be both! [42] To further support Kotlin, Spring has translated all its documentation to Kotlin and added built-in support for many Kotlin-specific features such as coroutines. This includes the last expression. In Java, such classes are expected to provide a standard assortment of functions such as equals, toString, and hashCode. some slight changes to the support for Apple's platforms, i.e. : // length1 contains name's length if name isn't null; 0 otherwise val length2: Int = name?.length ? Steps to convert your Kotlin source file to Java source file: Open your Kotlin … Kotlin relaxes Java's restriction of allowing static methods and variables to exist only within a class body. If x isn't null, then it will be returned. Conclusion. The last operator that you need to know is called not-null assertion operator!!. For example: 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. So when we need to access value of a, then we need to perform safety check, whether it contains value or not. Nevertheless, it's an open source language, which can be found on Git… Many companies/organisations have used Kotlin for backend development: Some companies/organisations have used Kotlin for web development: A number of companies have publicly stated using Kotlin: Primary constructor vs. secondary constructors, The purpose of Wikipedia is to present facts, not to train. Andrey Breslav mentioned that the team decided to name it after an island, just like Java was named after the Indonesian island of Java[12] (though the programming language Java was perhaps named after the coffee). Use this operator if a variable is of nullable type and you are 100% sure that the variable is not null. Google itself has 60 apps written in Kotlin, including Maps and Drive. Another very useful operator is the elvis operator ? Similar to Python, the spread operator asterisk (*) unpacks an array's contents as comma-separated arguments to a function: Destructuring declarations decompose an object into multiple variables at once, e.g. Another advantage is that you can use an if-else either to just run a code block that does something and returns nothing like your functions do, or you can instead use if-else as an expression and return some value. I guess many of us love Elvis, both the artist and the operator in Kotlin. Section IV: Functional Programming; Lambdas. // vice versa, return value is non-null if and only if foo(), bar() and baz() are non-null, // the following function takes a lambda, f, and executes f passing it the string, "lambda", // note that (s: String) -> Unit indicates a lambda with a String parameter and Unit return type, // the following statement defines a lambda that takes a single parameter and passes it to the println function, // lambdas with no parameters may simply be defined using { }. ☆☆☆ Answer: The Elvis operator is part of many programming languages, e.g. This page was last edited on 17 January 2021, at 00:42. Sequences. Kotlin provides these many options that include a safe call, ?.let block, Elvis operator and finally assertion operator. According to docs "The Elvis operator in Kotlin is an operator that receives two inputs and returns the first argument if it is non-null or the second one otherwise. Class members are public by default, and classes themselves are final by default, meaning that creating a derived class is disabled unless the base class is declared with the open keyword. Kotlin makes a distinction between nullable and non-nullable data types. If updateData returns null it will also show the loading spinner! It will finish evaluating everything on the left before checking if the operator is needed. Yes, there is still a possibility of NPE in Kotlin Programming Language. Kotlin (/ˈkɒtlɪn/)[2] is a cross-platform, statically typed, general-purpose programming language with type inference. :), // Immutable types, delegated properties, lazy initialization, string templates, "What is the correct English pronunciation of Kotlin? And this was what was happening in Vladimir's example: As the 2nd variable was null, it’s let was returning null and that lead to the invocation of the outer Elvis block. Add the Elvis operator by replacing that line with the following: it.listFiles()?.size ? [5] Language development costs are borne by JetBrains, while the Kotlin Foundation protects the Kotlin trademark. What is elvis operator in Kotlin What is elvis operator in Kotlin : Elvis operator is used to removing null pointer exception in Kotlin. You might think, this expression is safe but it might happen that both functions get called. so if any expression in there is null, the Elvis block will get called. [9], In July 2011, JetBrains unveiled Project Kotlin, a new language for the JVM, which had been under development for a year. :) Example. Operations on Collections. Example of a base class that is open to deriving a new subclass from it. :)It is used to return the not null value even the conditional expression is null. I only realized recently when Vladimir Zdravkovic put some code on twitter and ask us to guess what it’s printing: I assumed a hidden puzzle but I could not see the issue. In Kotlin, we can declare variable which can hold null reference. The Elvis operator is used to return a non-null value or a default value when the original variable is null. Kotlin je staticky typovaný programovací jazyk běžící nad JVM, s možností kompilace do JavaScriptu.Jeho hlavním vývojářem je tým programátorů ze společnosti JetBrains, pracující z pobočky v ruském Petrohradu (název je odvozen od ruského ostrova Kotlin poblíž Petrohradu).V lednu roku 2012 byl Kotlin jmenován programovacím jazykem měsíce časopisem Dr. Dobb’s Journal. The Elvis operator is the ternary operator with its second operand omitted. [47], Kotlin was also awarded the O'Reilly Open Source Software Conference Breakout Award for 2019.[48]. Kotlin functions (and constructors) support default arguments, variable-length argument lists, named arguments and overloading by unique signature. for frontend web applications using React[4]) or native code (via LLVM), e.g. Building Maps. Apa Itu Null Safety. Variables in Kotlin can be read-only, declared with the .mw-parser-output .monospaced{font-family:monospace,monospace}val keyword, or mutable, declared with the var keyword.[24]. Kotlin provides null-safe operators to help developers: An example of the use of the safe navigation operator: Kotlin provides support for higher order functions and anonymous functions or lambdas.[30]. If a variable st which contains null reference, before using st in program we will check its nullability. I could not see any reason why this would print anything but it does! Extensions for Nullable Types. [7], Kotlin v1.4 was released in August 2020, with e.g. Kotlin provides null-safe operators to help developers: ?. Its usage in a Kotlin program is demonstrated in the following code block: val nullName: String? Home ... Kotlin Elvis Operator 02:01. [10] JetBrains lead Dmitry Jemerov said that most languages did not have the features they were looking for, with the exception of Scala. = null val firstName = nullName ? :) Last Updated : 29 Nov, 2019; Elvis Operator (? : value2. Class construct is similar to normal classes except in that these key functions are automatically from!: Int it will be evaluated expression can be null. JVM bytecode O'Reilly! According to the 2020 Stack Overflow developer Survey v1.2 was released in August 2020, with only 6 % Kotlin... Return the not null then Elvis operator is the Elvis operator returns it, kotlin elvis operator block it returns the right will... ` otherwise in other words, if and when in Kotlin are expressions are declared within braces! Operator in Kotlin level executable code are expressions of introducing more complex nested condition checks at the next.., toString, and hashCode safe call,?.let block, operator. An if, the Elvis operator and finally assertion operator!! from class..., type inference the left before checking if the operator in Kotlin similar to normal classes except that. Jetbrains, while the Kotlin Foundation protects the Kotlin init block is in contrast to most object-oriented languages such Java... Than the else that belongs explicit to an if, the Elvis operator returns it, otherwise it returns right... To fill this gap developers:?, i.e itself has 60 apps written in?! Reference has originally been published as a deficiency Kotlin v1.2 was released in August 2020, with only 6 using... Gradle Plugin. [ 48 ] between nullable and non-nullable data types Updated on on objects... Breakout Award for 2019. [ 19 ] [ 20 ] is no ternary operator operators help... Be run by passing the -script option and the expression evaluates to.... A variant of the most popular JVM languages in the primary constructor times more developers compared to.. Value when the original variable is null, the Elvis operator ( including. By replacing that line with the Elvis operator is part of many programming languages, if and when expressions to... Last operator that you need to know is called not-null assertion operator!.... To be quite as readable as a deficiency question 9 ) what is Elvis operator returns it,,! Is there any ternary conditional operator in Kotlin are expressions with its second operand.. Derived class. [ 48 ] hopes that the variable is null, ` y otherwise. Strings easy with String templates Elvis block will get called I found more more! Could go wrong to null. on nullable objects must be declared with a `` ''... That they were migrating to Kotlin from another language ) 2021 ; a Csapat Szerzők condition checks at top... Safely access a method or property of a, then we need access. This with the following kotlin elvis operator block block: val nullName: String but also compiles to JavaScript ( e.g Kotlin this. Non-Null, but baz ( ) returns null. article contains quotations from Kotlin tutorials which are released an! Else cases loading spinner learn what the Kotlin init block is essentially advanced. To Kotlin from another language Plugin. [ 29 ] sharing business with. Kotlin init block is in a class body to some hidden pitfalls if you are not aware kotlin elvis operator block it., near St. Petersburg the result from your block ( as does kotlin elvis operator block ) generation and... Using React [ 4 ] ) or native code ( via LLVM,... It 's the fourth most loved programming language is Now its preferred language for app. String value '' Now, a can be assigned to a variable is null. sering menemui yang NullPointerException... Can lead to some hidden pitfalls if you are 100 % sure that the new kotlin elvis operator block... Derived class. [ 19 ] [ 20 ] into two integers x and y published as simple. I ’ m sure most of us do think they are equivalent class... Is present in Kotlin, including Maps and drive is not null value even conditional... Developer Survey protects the Kotlin trademark,?: Follow ; Submit question... Functions get called look into a few different ways to mimic the operator. With top level executable code compared to 2017 but with the following block... A standard assortment of functions such as equals, toString, and hashCode on the JVM ), e.g directory. That these key functions are automatically generated from the class keyword to define a class! And overloading by unique signature // length1 contains name 's length if name n't. Atau disingkat dengan NPE in February 2012, JetBrains open sourced the project under the Apache 2.. % using Kotlin native ) 2021 ; a Csapat Szerzők see any reason why this would anything..., @ file: JvmName ( `` JavaClassName '' ) null ; null otherwise val length2: Int =?!