Method 1: Using string.toDouble() : Kotlin provides a couple of functions for the string class. This document is not a part of Khan Academy’s official product offering, but rather an internal resource that we’re providing “as is” for the benefit of the programming community. in the string. Nested expressions. Binary search implementation in Kotlin for a list of custom objects. Python Basics Video Course now on Youtube! In Kotlin, additionally, we have triple-quoted raw Strings that can contain special characters without the need for escaping them. For checking substring in a string ignoring case, the only thing we need to do is pass true instead of false as the above example. Basics. Kotlin program of checking null in conditions ... GeeksforGeeks String of length 13 null Null String Note that we have used if-else block to check the nullability. NOTE: need to use outer single quote string in order to use double quote to represent empty string '@{viewModel.username.equals("") ?View.GONE : View.VISIBLE}' NOTE: isNullOrEmpty (Kotlin) doesn’t work for Data Binding. New Project and fill all required details to create a … As we are aware every programming language gas equal to an operator ( == ) to compare two things. Watch Now. Exploring ArrayList Functions. ... As we observed before, let's think that project has a lot of types, which can be marked as "non-empty string". or we can call the toRegex method on a String: "a[bc]+d? Exploring ArrayList Functions. Idioms. In addition, it is not required that the cases are constant expressions as in Java. We've also created a function isNullOrEmpty() which checks, as the name suggests, whether the string is null or empty. For now there are two the most easy approaches to compile Kotlin in the runtime: you can use Kotlin Compiler directly or you can use jsr233 wrapper. What's New. Here's the equivalent Java code: Java program to remove all whitespaces kotlin documentation: Tableaux génériques. public class User { private final String name; public User(String name) { this.name = name; } public String getName() { return name; } } Since Kotlin doesn’t know about the nullability of the member variable name, It allows all operations on this variable. 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Compare the syntax of Kotlin vs C#. In the above written examples we have made and mutableMapOf. Packages and Imports. Kotlin String has methods, isBlank() and isEmpty(). Then, we replace it with "" (empty string literal). A possibility is to call the Regex constructor: Regex("a[bc]+d?") String.length property returns the number of characters in the string. Kotlin for Python developers. This example demonstrates how to Check if Android EditText is empty in Kotlin. Kotlin for Data Science. Kotlin for Android. in the string. To find the length of string in Kotlin language, you can use String.length property. Kotlin also has a compareTo method which we can use to compare the order of the two strings.Similarly as the equals method, the compareTo method also comes with an optional ignoreCase argument:. println(str == null || str.isEmpty()) // true. The same practice led me t o use joinToString() Kotlin method to reduce my for loop usage to create a list of comma separated “string” values to be passed in a SQLite query. Kotlin String. Unit is a Kotlin singleton object, and is handled equally with other Kotlin objects. All right, It’s nice that Kotlin disallows method calls and property access on nullable variables to guard against NullPointerException errors. Syntax of List.isEmpty() The syntax of List.isEmpty() function is. Kotlin is like C#. This tutorial is all about Kotlin ArrayList. Create Empty mutableMapOf. The library actually contains functions isNullOrEmpty, and isNullOrBlank, which checks whether string is null, or empty, or blank. ... Kotlin is a modern programming language with features that make it easier to be productive in writing concise code, which is also less prone to errors. Using “==” Operator:-. Compare the syntax of Kotlin and C# through short code examples. If expression is pretty … One of them is safe call ?. It returns a decimal number if it can, or it returns null if there's a problem. Kotlin List.isEmpty() Function. We've used regular expression \\s that finds all white space characters (tabs, spaces, new line character, etc.) Getting Started. Basic Types. Creating an empty String: To create an empty string in Kotlin, we need to create an instance of String class. If you need to annotate your Kotlin classes with an @JSON annotation or otherwise, you need to add KotlinJsonAdapterFactory as well. In this tutorial, we will learn several types of expressions used in Kotlin. Method 1: Using string.toDouble() : Kotlin provides a couple of functions for the string … The Kotlin builtin Unit type is also serializable. In this tutorial, we’re gonna look at overview of Kotlin Queue interface and some examples that show how to work with Kotlin Queue such as define, initialize, add or remove items, peek, poll methods. str1 contains null value and str2 is an empty string. © Parewa Labs Pvt. To use the nullable type, I use a workaround based on the private serialized string and typed getter/setter. Kotlin extension to split string and filter out empty string. In this tutorial, we will discuss how to compare strings in kotlin? How to validate Email Address in Android on EditText using Kotlin? This tutorial is all about Kotlin ArrayList. Check if value is empty in JavaScript; How to check if an Android application is running in the background using Kotlin? You may need to find the string length during scenarios like: string validation; check if string is empty; check if string is exceeding an allowed length; etc. We can easily access the element of the string using string[index]. If you like we can create a String mutableMapOf or int mutableMapOf. What's New in 1.3. public fun < T > arrayOf (vararg t: T): Array < T > Donc, pour créer un tableau vide de chaînes, vous pouvez écrire val emptyStringArray = arrayOf < String >() This article explores different ways to check for a null or empty List in Kotlin. Use empty strings as the default values. To understand the arraylist concepts in details. Is there a way to make the code work without changing var name: String to var name: String?. If you look at the code for String.Empty it actual refers to “” in the background so, like @ilogico, I could never understand the reason why some people insisted on using String.Empty instead. Conceptually, a singleton is a class with only one instance, meaning that state does not define the object, but the object defines its state. We will learn different ways to solve this problem. Join our newsletter for the latest updates. We've used regular expression \\s that finds all white space characters (tabs, spaces, new line character, etc.) int, string, float etc. À la fin (juin 2015), il existe une fonction de bibliothèque standard Kotlin. Basic Syntax. Sometimes, it sends an empty string instead null. In this program, you'll learn to remove all whitespaces in a given string using regular expressions in Kotlin. In the above written examples we have made and mutableMapOf. One of the common operation when working with strings is to extract a substring of another string. I'm a beginner to Kotlin and am loving it so far. Then, we replace it with "" (empty string literal).. 1. Kotlin™ is protected under the Kotlin Foundation and licensed under the Apache 2 license. There are several subString methods added to Kotlin String class as extension functions and we’re going to see them one-by-one. There are different methods to declare String, some of them are listed below: #1. Returns this array if it's not empty or the result of calling defaultValue function if the array is empty. ... // read-only empty list var empty = Enumerable.Empty(); ForEach. Using arrayOf : Python - Check if dictionary is empty; How to check if a C# list is empty? in the string. Supported and developed by JetBrains Supported and developed by JetBrains In this kotlin programming tutorial, we will learn how to check if a substring exists in another string or not. You can treat it as nullable or non-nullable, but the compiler won’t enforce anything. We can create one in several ways. To remove last N characters from a String in Kotlin, use String.dropLast() method. Kotlin. This time let’s create map. Kotlin arrays and Kotlin strings are two commonly used data types. This would be more comprehensive, so that a nullable String could also use this function. By Aasmund Eldhuset, Software Engineer at Khan Academy.Published on November 29, 2018. If you don't have this file, create a new Kotlin file and call it MyName.kt. Unlike Java, Kotlin doesn’t require a new keyword to instantiate an object of a class.. Kotlin String class has one method called contains to check if a string contains another substring or not. Throws an IllegalStateException if the value is null. Here's the equivalent Java code: Java program to remove all whitespaces, Count the Number of Vowels and Consonants in a Sentence. Calling toDouble() on a string that is empty or a string that doesn't represent a valid decimal number doesn't work. Define a data class for the name and nickname. The Kotlin List.isEmpty() function checks if the list is empty or not. But you use such functions in Kotlin from the standard library by default. Kotlin provides different ways to generate string arrays and we can use them to create one empty string array. I'd like the funtionality of the following: "If readLine() is null or empty assign default value, else parse readLine()" And so far, what I've come up with is this: 2. Kotlin for JavaScript. Otherwise returns the not null value. To understand the arraylist concepts in details. ".toRegex() Finally, we can use a static factory method: Regex.fromLiteral("a[bc]+d?") Iterate given string … Kotlin – Remove Last N Characters from String. What's New in 1.2. Example: val newString = “Example” Declaring String in Kotlin Using Various Methods. Coding Conventions. The Kotlin List.isEmpty() function checks if the list is empty or not. This article explores different ways to check if a string is empty or null in Kotlin. The syntax is simple, just use the keyword ArrayList and create a arraylist. Kotlin Array is mutable in nature i.e. A list is empty if and only if it contains no elements. To use the nullable type, I use a workaround based on the private serialized string and typed getter/setter. Program to Reverse a string Pseudo Algorithm. kotlin.internal.InlineOnly public inline fun CharSequence?.isNotEmpty(): Boolean = this != null && length > 0. Kotlin Array; Kotlin Range; Control Flow. Working with Nullable Types. Environment Kotlin 1.2.0 Empty Empty means no-content. Fortunately Kotlin also provides a method called toDoubleOrNull() which handles these problems. I wrote about their difference. Don't take language likeness comparison too seriously. If you are starting with Kotlin, ... Array) { runApplication(*args) } Compared to Java, you can notice the lack of semicolons, the lack of brackets on empty class (you can add some if you need to declare beans via @Bean annotation) and the use of runApplication top level function. We can create an empty mutableMapOf of any type. Therefore, we can create common mapper for them: We will learn how to check if the string contains a substring by ignoring all case of each character during the checking and by not ignoring the case. You could also put an expression within a string declaration, by placing the expression within { } and using the $ symbol before it. If expression 2. Multiplatform. length: This is a property that can be accessed using the dot operator on the String.Returns the number of characters present in a string. I'm curious if Kotlin has a quick and simple solution to checking user input/strings for emptiness. First, a sample list to work with: val nums = listOf(1,2,3,4,5) Then here’s the joinToString example: Here's the equivalent Java code: Java program to remove all whitespaces Kotlin check if a string is numeric : In this post, I will show you how to check if a string is numeric or not in Kotlin. Specifically for this task, I have to swap the name in order to let you implement it yourself. val str = "". Example: val newString = “Example” Declaring String in Kotlin Using Various Methods. Kotlin check if a string is numeric : In this post, I will show you how to check if a string is numeric or not in Kotlin. import kotlin.text.regex var string = /* some string */ when { Regex( /* pattern */ ).matches(string) -> /* do stuff */ Regex( /* pattern */ ).matches(string) -> /* do stuff */ /* etc */ } Using the visitor pattern: Has the benefit of closely emulating the "argument-ful" when syntax. 6 ways to add items to a list in Kotlin. Create Empty mutableMapOf. Kotlin for Native. Kotlin – If expression. but before figuring out the difference among … We've used regular expression \\s that finds all white space characters (tabs, spaces, new line character, etc.) var a = String() Here’s how in Kotlin you can describe a String attribute. assertTrue { first.compareTo(second) == 0 } assertTrue { first.compareTo(firstCapitalized) == 32 } assertTrue { firstCapitalized.compareTo(first) == -32 } assertTrue { … var variable_name = String() String elements and templates – String Element – The character, digit or any other symbol present in string is called as element of a String. Kotlin Script Evaluation. Step 1 − Create a new project in Android Studio, go to File? Then, we replace it with "" (empty string literal).. The first argument is the substring that we need to check. Kotlin if expression; Kotlin when expression; Kotlin for loop; Kotlin while loop; Kotlin do-while loop; Kotlin continue; Kotlin break; Kotlin Function. If..else if..else expression 4. String comparison in kotlin. Kotlin ArrayList Examples. In this article, you will learn about how to use arrays and strings in Kotlin. Les tableaux génériques de Kotlin sont représentés par Array.. Pour créer un tableau vide, utilisez la fonction de fabrique emptyArray(): . var str: String = "Hello" Create an empty string which don’t contain anything inside the string. An empty string is a string of zero length, represented as "". Kotlin makes working with Strings easy with String templates. var s = String() //creates an empty string. Here’s a little Kotlin joinToString example. When you run the program, the output will be: In the aboe program, we use String's replaceAll() method to remove and replace all whitespaces in the string sentence. Related Post: Kotlin Priority Queue tutorial with examples Overview A Queue is just like a queue in real-life. Similarly, in Kotlin, I can’t really see why: Explore some of Kotlin's null safety operators, like safe calling, rude, and elvis, to see how you can more fully bring over your Java Optional experience. Cases in Kotlin can be dynamic expressions that are evaluated at runtime. In contrast, Kotlin allows us to use the when block with any built-in or user-defined type. String templates allow you to reference variables inside string declarations by using the $ symbol before the variable. 4. fun main() {. Output: Reversed: !maR iH 1. We will learn different ways to solve this problem. var a = String() Here’s how in Kotlin you can describe a String attribute. Example: Input: str = "" Output: True Program to check for Empty, Blank or NULL string in Kotlin So, in this quick article, we’ll talk about how to use different substring methods in Kotlin. fun CharSequence .splitIgnoreEmpty( vararg delimiters: String): List { return this .split(*delimiters).filter { it.isNotEmpty() } } Logically Not Empty is definitely Not Null. Three different ways to create an empty string array in Kotlin. If string contains null then it executes the if block else it executes the else block. If..else expression 3. The same practice led me t o use joinToString() Kotlin method to reduce my for loop usage to create a list of comma separated “string” values to be passed in a SQLite query. Equality of String in kotlin. There are still few techniques for using or accessing the nullable variable. Write a Kotlin Program to reverse string with example. val empty = emptyArray() A list is empty if and only if it contains no elements. Kotlin for Server Side. Given a string, we have to check whether it is an empty, blank or NULL string. How to check if a list is empty in Python? What's New in 1.1. Alternatively, you can use isEmpty () function to check for an empty string in Kotlin. If you want to check for null and empty, it’s better to use TextUtils.isEmpty instead. In JSON, objects are serialized as empty … val countriesArrayList = ArrayList() We have created an empty arrayList using constructor. Exemple. For example, “1.2” is a numeric string but 1.2x is not. val countriesArrayList = ArrayList() We have created an empty arrayList using constructor. Coroutines. In this tutorial, we will go through syntax and examples for List.isEmpty() function. Sometimes, it sends an empty string instead null. 3. How to check if String is empty in Java? Important Properties and Functions of Kotlin String. Creating an empty String: To create an empty string in Kotlin, we need to create an instance of String class. The syntax is simple, just use the keyword ArrayList and create a arraylist. If you find any errors, please submit an issue or a pull request. Like other languages, Array in kotlin is a collection of similar data type i.e. It’s a First […] Since Kotlin knows beforehand which variable can be null and which cannot, It can detect and disallow calls which could result in NullPointerException at compile-time itself. Example 1: Check if List is Empty 1. isNullOrEmpty() function From Kotlin 1.3 onwards, the recommended approach is to use isNullOrEmpty() method to check for an empty or null list in Kotlin. In this post, I will show you three different ways to do that with examples. Kotlin ArrayList Examples. Try to run both examples we have shown above and drop one comment below if you have any queries. This time let’s create map. In kotlin we use expressions to control flow in the program. Unfortunately, not every API sends valid JSON. Kotlin: Convert a list to a String (joinToString syntax/example) By Alvin Alexander. 5 different ways in Kotlin to find a string in a list of strings . To check for null as well, it should be preceded by a null check. This would be more comprehensive, so that a nullable String could also use this function. List.isEmpty() function returns true if the collection is empty (contains no elements), false otherwise. It takes two arguments : Below examples will add more clarity to you : Let’s try to implement the contains method by not ignoring all character case : The output of the above program will look like below : eval(ez_write_tag([[250,250],'codevscolor_com-medrectangle-4','ezslot_4',140,'0','0']));As you can see, if we are passing false to the contains method, it checks the character case while comparing. 1. Kotlin Script Evaluation. This article explores different ways to check for a null or empty List in Kotlin. and another one is null check !! we can perform both read and write operation on elements of array. Kotlin array is represented by Array class, that has get and set functions, size property and other member functions. 1. isNullOrEmpty() function From Kotlin 1.3 onwards, the recommended approach is to use isNullOrEmpty() method to check for an empty or null list in Kotlin. In Java, the switch statement can only be used with primitives and their boxed types, enums, and the String class. L lateinit. Last updated: December 2, 2018. Given a string str1, and if we would like to remove last n characters from this string str1, call dropLast() method on string str1 and pass the integer n as argument to the method as shown below.. str1.dropLast(n) var variable_name = String() String elements and templates – String Element – The character, digit or any other symbol present in string is called as element of a String. isEmpty is the same as comparing to zero string (value For example, “1.2” is a numeric string but 1.2x is not. A custom serializer for classes, containing many members, is more complex than this workaround. Save from a difference explained in the next section, these options are … The program will take the strings as input from the user and print out the result. Kotlin String Length. Ltd. All rights reserved. data class MyName(var name: String = "", var nickname: String = "") Step 2: Add data to the layout 1. 5 different Kotlin program to iterate through a mutablelist. Kotlin String; Kotlin Array. Unfortunately, not every API sends valid JSON. We can create an empty mutableMapOf of any type. list.isEmpty() Return Value. A custom serializer for classes, containing many members, is more complex than this workaround. We have learned how to check if a substring exists in a string or not in Kotlin. It checks it using a null check using != null and isEmpty() method of string. Use a temp variable result that stores reversed string. How to sort a kotlin map by value. So, in this quick article, we’ll talk about how to use different substring methods in Kotlin..subString(startIndex: Int) Method. Example: ${user.firstName}. Regular expressions are instances of the kotlin.text.Regex class. 1. isNullOrEmpty() function The standard approach in Kotlin to check for a null or an empty string is … Input: Hello World Output: dlroW olleH Input: Hi Ram! Convert array to arraylist and vice-verse, Find the Frequency of Character in a String. It is a character sequence of zero characters. If you like we can create a String mutableMapOf or int mutableMapOf. Kotlin vs C#. There are several subString methods added to Kotlin String class as extension functions and we’re going to see them one-by-one. var str: String = "Hello" Create an empty string which don’t contain anything inside the string. 1. Initialize it with empty string. Used regular expression \\s that finds all white space characters ( tabs,,! Going to see them one-by-one learn how to check for null as well that! To iterate through a mutablelist ] +d? '' objects are serialized as empty … Kotlin class... Above and drop one comment below if you find any errors, please submit an or! A [ bc ] +d? '' decimal number if it can, or empty or... Unit is a numeric string but 1.2x is not call the Regex constructor: Regex ``. Only if it contains no elements null or empty list in Kotlin you can treat it as or. Kotlin – remove Last N characters from a string, string > mutableMapOf show you different. Isnullorempty ( ) function it executes the else block any queries in Android on using! Empty … Kotlin Script Evaluation Kotlin strings are two commonly used data types swap the name in order to you! Hello World Output: dlroW olleH input: Hi Ram represented as `` '' //creates... Substring exists in a list of custom objects ) to compare two things it ’ s to... Any errors, please submit an issue or a string is a numeric string but is. And Kotlin strings are two commonly used data types block else it executes the block. Charsequence?.isNotEmpty ( ) function is str == null || str.isEmpty ( function... Library by default easily access the element of the string using string [ index ] Kotlin... Valid decimal number does n't work the next section, these options …! Still few techniques for using or accessing the nullable variable otherwise, you can describe string. Created an empty string literal ) an empty string: to create one empty string literal ) difference explained the! Typed getter/setter the name and nickname an empty string in Kotlin is a numeric string but 1.2x not! Allow you to reference variables inside string declarations by using the $ symbol before the variable, please an. Based on the private serialized kotlin if empty string and typed getter/setter or non-nullable, the..., 2018 zero length, represented as `` '' ( empty string to! Use this function for classes, containing many members, is more complex this. Null string order to let you implement it yourself next section, these options are … Throws an IllegalStateException the... Addition, it is not required that the cases are constant expressions as Java! Addition, it sends an empty, or blank ) method of in! By using the $ symbol before the variable reverse string with example be preceded by null. Us to use arrays and Kotlin strings are two commonly used data types print out the result number of and! Running in the above written examples we have learned how to use TextUtils.isEmpty instead any,! Still few techniques for using or accessing the nullable type, I a! Private serialized string and filter out empty string other languages, array Kotlin... Olleh input: Hello World Output: dlroW olleH input: Hello World Output dlroW! Convert array to ArrayList and vice-verse, find the Frequency of character a. On a string in Kotlin, additionally, we have shown above and drop one comment below you... Are two commonly used data types? '' will learn how to use substring! 'Ll learn to remove Last N characters from a difference explained in above. S better to use arrays and we ’ re going to see them one-by-one: dlroW olleH input: Ram. Regex constructor: Regex ( `` a [ bc ] +d? ). Kotlin is a string that does n't work is null, or empty var! To split string and typed getter/setter space characters ( tabs, spaces, new line character etc! Out the result that are evaluated at runtime JSON, objects are as! It executes the else block mutableMapOf or int mutableMapOf created an empty string: to create an string... All white space characters ( tabs, spaces, new line character, etc. Regex. Programming language gas equal to an operator ( == ) to compare things... Or a string, string > ( ) Finally, we will go through syntax and examples for List.isEmpty )... Nice that Kotlin disallows method calls and property access on nullable variables guard. Object of a class string has methods, isBlank ( ) method or blank contains functions isNullOrEmpty, the. String instead null we are aware every programming language gas equal to an operator ==! Figuring out the difference among … Kotlin Script Evaluation string mutableMapOf or int mutableMapOf annotation or otherwise you. The Regex constructor: Regex ( `` a [ bc ] +d ''. Str.Isempty ( ) create empty mutableMapOf of any type any type to through. The equivalent Java code: Java program to remove all whitespaces Kotlin – remove Last N characters from string workaround. As the name suggests, whether the string class has one method called contains to check Android! And typed getter/setter could also use this function a ArrayList classes with an @ JSON or. Addition, it sends an empty string ) the syntax of List.isEmpty ( ) we have made < int string. Than this workaround = “ example ” Declaring string in Kotlin is a string that does n't a... Above and drop one comment below if you need to annotate your Kotlin classes an... Be dynamic expressions that are evaluated at runtime can perform both read write... Inline fun CharSequence?.isNotEmpty ( ) and isEmpty ( ) we have made < int, string (. Licensed under the Apache 2 license under the Kotlin List.isEmpty ( ) a! Options are … Throws an IllegalStateException if the list is empty to find length. String is empty if and only if it contains no elements true if the collection is empty or null Kotlin. A couple of functions for the string using regular expressions in Kotlin, additionally we... Suggests, whether the string class here 's the equivalent Java code: Java program to iterate through a.... Create a ArrayList aware every programming language gas equal to an operator ( ). Kotlin singleton object, and the string using string [ index ] that we need check., the switch statement can only be used with primitives and their boxed types enums. Vice-Verse, find the length of string contains null value and str2 is empty! When block with any built-in or user-defined type new keyword to instantiate object... Require a new project in Android Studio, go to File Kotlin provides ways... Find the Frequency of character in a string that does n't represent a valid decimal number it. An @ JSON annotation or otherwise, you need to create an empty, or blank containing many,! A substring exists in a string, you 'll learn to remove all,... List var empty = Enumerable.Empty < string, we need to create an empty in. Easy with string templates = Enumerable.Empty < string > ( ) function a. Through syntax and examples for List.isEmpty ( ) ; ForEach many members, is more complex than workaround! Take the strings as input from the standard library by default you want to if. Array in Kotlin you can use String.length property string of zero length, represented ``..., these options are … Throws an IllegalStateException if the collection is empty in Kotlin a [ bc +d. With an @ JSON annotation or otherwise, you need to check <. [ index ] suggests, whether the string class boxed types, enums, and the is... Software Engineer at Khan Academy.Published on November 29, 2018 isBlank ( ) method of string a valid decimal does. Provides different ways to check for null as well you implement it yourself checking user for... Elements ), il existe une fonction de kotlin if empty string standard Kotlin Consonants in a in... That stores reversed string, 2018 string could also use this function quick and simple solution to user. In python list is empty in Kotlin to iterate through a mutablelist to do that with examples compiler won t. Can describe a string that is empty ; how to check for null and empty, blank or null.... ’ s how in Kotlin ( contains no elements ), false.! Dlrow olleH input: Hello World Output: dlroW olleH input: Hello World:! In addition, it sends an empty string literal ) disallows method calls and property access on nullable to... Line character, etc. members, is more complex than this workaround collection of similar data i.e. Syntax of Kotlin and am loving it so far joinToString syntax/example ) by Alvin Alexander a keyword! Possibility is to call the toRegex method on a string mutableMapOf or int mutableMapOf as `` (. It using a null or empty list var empty = Enumerable.Empty < string mutableMapOf! Are serialized as empty … Kotlin Script Evaluation nullable type, I have to check for a list of objects... +D? '': to create an empty string instead null use function... > mutableMapOf à la fin ( juin 2015 ), il existe une fonction de standard... Them are listed below: # 1 Finally, we can create an empty ArrayList using constructor these. Of any type methods added to Kotlin string class of Kotlin and C # list is empty CharSequence...

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