Found 417 Articles for Kotlin

The concept of exception in Kotlin is very much same as it is in Java. All the exceptions in Kotlin are the descendants of the Throwable class. @Throws annotation indicates what exceptions should be declared by a function when compiled to a JVM method.Example – Throwing exception using a methodIn this example, we will create a scenario where we will generate a logical arithmetic exception, but we will try to throw a different exception using the @throws annotation and a function call.import java.io.* import kotlin.jvm.Throws fun main(args: Array) {    val item=0    var result=0    try {   ... Read More

List denotes a List collection of generic data type. By , we understand that the List does not have any specific data type. Let's check how we can initialize such a collection in Kotlin.List can be of two types: immutable and mutable. We will see two different implementations of initializing List.Example – Initialize List ~ Immutable ListOnce a list is declared as Immutable, then it becomes read-only.fun main(args: Array) {    var myImmutableList = listOf(1, 2, 3)    // Convert array into mutableList    // Then, add elements into it.    myImmutableList.toMutableList().add(4)    // myImmutableList is not a ... Read More

A Map is a collection where data is stored as a key-value pair and the corresponding keys have to be unique. A HashMap is a collection class based on MutableMap interface and it does that by implementing the MutableMap interface of HashTable.Kotlin provides four types of constructors to define and manipulate a HashMap.Example – Map Creation and Iteration in KotlinIn this example, we will be creating a Map called "subject" and we will be iterating through it.fun main(args: Array) {    // Declare HashMap    var subject : HashMap       = HashMap ();    // Assigning ... Read More

In order to remove extra whitespaces in a string, we will use the replace() function along with toRegex() function from the String class. To replace all the consecutive whitespaces with a single space " ", use the replace() function with the regular expression "\s+" which matches with one or more whitespace characters.Example – Removing extra whitespaces in KotlinTake a look at the following example −fun main(args: Array) {    var myString = "Removing ex tra spa ce from String"    println("Input String: " + myString)    // removing duplicate whitespace    println("Extra whitespaces removed: "    + myString.replace("\s+".toRegex(), " ... Read More

Kotlin provides a set of bitwise operators that we can use on integers. These operators can be applied only to Int and Long type variables. Here is the list of bitwise operations available in Kotlin −shl(bits) – Signed Shift leftshr(bits) – Signed shift rightushr(bits) – Unsigned shift rightand(bits) – Bitwise AND operatoror(bits) – Bitwise OR operatorxor(bits) – Bitwise XORinv() – Bitwise inversionKotlin does have functions for each of them.Example: Bitwise Operators in KotlinThe following example shows how you can implement the bitwise operators in Kotlin.import java.lang.* fun main(args: Array) {    val value = 5    println("Input value: " + ... Read More

return@ is a statement in Kotlin which helps the developers to return a function to the called function. In simple words, return@ can return any value, anonymous function, simple inline function, or a lambda function.Example – return in Kotlinfun main(args: Array) {    val s = message()    println("Message = $s") } fun message():String{    return "Hello Kotlin! This is a returned message." }OutputIt will produce the following output −Message = Hello Kotlin! This is a returned message.Example – Kotlin Labeled returnNow "return@" helps to control the flow to a specific level inside the code. In Kotlin terminology, it is ... Read More

Kotlin ArrayList class can be used in order to create an empty arrayList. It would be a dynamic array which means it will automatically expand as we add data into it. An ArrayList is an ordered sequence of elements, however, unlike simple arrays, an ArrayList can contain data of multiple data types.The function definition of arrayList goes like this −fun arrayListOf(): ArrayListIt returns an empty new ArrayList. If a number is provided as the argument, then it will return an arrayList with the given elements.Example: Initialize an empty array in KotlinThe following example demonstrates how you can create a ... Read More

In this article, we will see how we can convert an ArrayList in Kotlin to a String. In order to do so, we will use a String function called joinToString() that is provided by the Kotlin library. Its definition goes like this −fun Array.joinToString(    // the String will be separated by comma    separator: CharSequence = ", ",        // prefix to the String    prefix: CharSequence = "",        // postfix to the String    postfix: CharSequence = "",        // This number of elements will be printed;    // the ... Read More

In this article, we will see how we can get the type of a class that is used in Kotlin. There are no direct ways to do this in Kotlin. In order to check the generic type, we need to create an instance of the generic class and then we can compare the same with our class.ExampleFor this example, we will create a generic class of type and we will pass our variable inside this class in order to check its type.class MyGenericClass(val myclass: Class) {    companion object {       inline operator fun invoke() = MyGenericClass(T::class.java)   ... Read More

Java provides a String method called equalsIgnoreCase() which helps developers to compare two strings on the basis of their content. This comparison is case-insensitive, that is, it ignores whether the strings are in uppercase or lowercase and just compares the string values. In this article, we will see how we can implement the same functionality in Kotlin.Example – equalsIgnoreCase in JavaThe following example demonstrates how equalsIgnoreCase() works in Java.public class MyClass {    public static void main(String args[]){       String s1="TutorialsPoint";       String s2="tutorialspoint";       System.out.println("String 1: " ... Read More