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Articles by Soumak De
62 articles
Best way to null check in Kotlin
In any programming paradigm, it is mandatory to check "null safety" in order to prevent runtime errors. In this article, we will see different ways to check "null safety" in Kotlin. Example - Using if…else In most of the programming languages, we have the "if" keyword to check conditions. In Kotlin too, we can use the "if-else" clause to check the null safety of a variable. fun main() { val name="TutorialsPoint.com" //null check if (name != null) { println(name) ...
Read MoreHow to find the number of repeated values in a Kotlin list?
In this article, we will see how to find the number of repeated values in a Kotlin list.Example – Finding Repeated Values Using groupingBy()The Kotlin library provides an inline function called groupingBy() which creates a grouping source from an array to be used later with one of the group-and-fold operations using the specified keySelector function to extract a key from each element.The function declaration of groupingBy() looks like this −inline fun Array.groupingBy( crossinline keySelector: (T) -> K ): GroupingIn this example, we will create a list of values and implement groupingBy() in the list.fun main(args: Array) { ...
Read MoreHow to create a mutable list with repeating elements in Kotlin?
A Mutable List is an interface and generic collection of elements. Once a collection is declared as mutable, it becomes dynamic and we can modify its data as per requirement. A mutable list grows automatically in size as we insert new elements into it. The Mutable List inherits form the Generic class.Example – Creating a Mutable List in KotlinIn order to create a mutable list of repeating elements, we will be using Kotlin List(). By definition, it looks like this−inline fun List( size: Int, init: (index: Int) -> T ): ListAs we pass an initial default value, ...
Read More@Throws Annotation in 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 MoreHow to initialize List<T> in Kotlin?
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 MoreHow to replace duplicate whitespaces in a String in Kotlin?
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 MoreHow to use Java's bitwise operators in Kotlin?
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 MoreWhat does "return@" mean in Kotlin?
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 MoreHow to initialize an empty array list in Kotlin?
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 MoreHow to convert an ArrayList to String in Kotlin?
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 ...
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