Found 417 Articles for Kotlin

In this article, we will see how to convert a String to Long in Kotlin using a library function. There are multiple ways to do it. Let's take a couple of examples to demonstrate how it's done.Example - using toLong()toLong() is a function that provides the most convenient way to convert a string to a long. In the following example, we will see how we can use toLong() to convert our String.fun convertToLong(s: String) {    try {       val value = s.toLong()       println("The Long value is: $value")    }    catch (ex: ... Read More

Varargs, also known as "variable arguments" is a new mechanism in Java by which methods in Java can accept zero or multiple number of arguments. Before this mechanism, the only option available to achieve this type of functionality was "method overloading", but that also required multiple lines of boilerplate code.In this article, we will see how we can use Varags in Kotlin to call a function multiple times based on different types of arguments. The following example demonstrates how we can use this Varags keyword.Examplefun main() {    // calling the function with 4 arguments and    // passing 3 ... Read More

In Kotlin, you can easily call another function by just importing the same in the current Kotlin file where your main function is running. Whatever the function we are declaring in a Kotlin file will be compiled into a static method by default, and it will be placed under the same package. The name of the newly created file will be renamed as the First letter capitalized and ".kt" extension replaced with the "Kt" suffix.In this article, we will try to get an insight into how you can use Kotlin extension methods from a Java file.ExampleLet's create a Kotlin file ... Read More

In this article, we will see how we can convert a List to a Map using various options provided by the Kotlin Library.Example: Using associate()The most standard way of converting a list into a map is by using the associate() function. This function takes a list of items as an argument and it returns a map containing key-value pairs. In the following example, we will see how it works.Exampledata class mySubjectList(var name: String, var priority: String) fun main() {    val mySubjectList: List = listOf(       mySubjectList("Java", "1"),       mySubjectList("Kotlin", "2"),       mySubjectList("C", ... Read More

Kotlin is based on Java, hence we can use Java-based library functions to delay a function call. In this article, we will be using a Java library function to delay the function call using Timer() and schedule().Exampleimport java.util.Timer import kotlin.concurrent.schedule fun main(args: Array) {    // Execution starting point    println("Hello world!!")    // Delay of 5 sec    Timer().schedule(5000){       //calling a function       newMethod()    } } fun newMethod(){ println("Delayed method call!") }OutputOnce executed, the above piece of code will yield the following output −Hello world!! Delayed method call!

String is a collection which is implemented using String class. As per the Kotlin documentation, a string can be defined as follows −Class String : Comparable, CharSequenceIn Kotlin, a string is a collection of characters. Strings are immutable in nature which means they are read-only. The length and elements of a string can be modified once declared.In Java, we have an option to create an empty String array by defining it like String[]. In this article, we will see how we can achieve the same using Kotlin library function.Example: Using arrayOf()Kotlin library provides a function to create an array of ... Read More

Kotlin provides multiple ways to generate a random number. In this article, we will see different ways to generate a random number and access it throughout the program.Example – Using Random classRandom() is an abstract class which generates random numbers with the given conditions. It can be accessed after importing Kotlin.random.Random.As per the Kotlin documentation, the companion object Random.Default is the default instance of Random class. In the following example, we will generate a list of random values with int (1-30) .Exampleimport kotlin.random.Random fun main() {    val myRandomValues = List(5) { Random.nextInt(0, 30) }    // Prints ... Read More

Sometimes it becomes necessary to access the index of an array. In this article, we will see how we can access the index of an array in Kotlin while using forEach loop.Example: Using forEachIndexed()nstead of using forEach() loop, you can use the forEachIndexed() loop in Kotlin. forEachIndexed is an inline function which takes an array as an input and its index and values are separately accessible.In the following example, we will traverse through the "Subject" array and we will print the index along with the value.Examplefun main() { var subject = listOf("Java", "Kotlin", "JS", "C") ... Read More

"reified" is a special type of keyword that helps Kotlin developers to access the information related to a class at runtime. "reified" can only be used with inline functions. When "reified" keyword is used, the compiler copies the function’s bytecode to every section of the code where the function has been called. In this way, the generic type T will be assigned to the type of the value it gets as an argument.ExampleIn this example, we will see how "reified" is helpful to re-use our code and use the same function to perform similar kind of operation regardless of its ... Read More

In Kotlin, "!!" is an operator that is known as the double-bang operator. This operator is also known as "not-null assertion operator". This operator is used to convert any value to a non-NULL type value and it throws an exception if the corresponding value is NULL. In the following example, we will see how to use this double-bang operator.Example 1In this example, we will consider a variable "name" and as a programmer, we want to throw a NULL pointer exception whenever the value of "name" is NULL. Now, execute the following codefun main(args: Array) { var name: ... Read More