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Page 26 of 148
How to implement Builder pattern in Kotlin?
In object-oriented programming, the creation of objects is very easy via constructors when the object definitions are simple, but sometimes, it may so happen that the constructors need more variables or functions in order to initialize an object. In such cases, the "builder pattern" comes into picture which helps programmers to create small units of different objects and create a final object.A builder pattern provides an API to construct an object step- by-step.Builder patterns are particularly useful when objects need to be created dynamically.Note that it is not recommended to use builder patterns in Kotlin because we can get the ...
Read MoreHow to convert a Kotlin source file to a Java source file?
Kotlin is a statistically typed language that runs on JVM. Once a Kotlin file is compiled, it creates a .class file that can be executed on the JVM. In this article, we will see how we can convert a Kotlin source file to a Java source file. In this process, we will be taking help from different online Decompilers available on the Internet.Open VS Code.Go to the "extension" section and install "Kotlin language support for VS Code" and "Code Runner". We need these two extensions to run Kotlin in VS code environment.Install Kotlin compiler in your system as per the ...
Read MoreConvert Kotlin Array to Java varargs
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 MoreAccessing Kotlin extension functions from Java
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 MoreHow to call a function after a delay in Kotlin?
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!
Read MoreWhat's the Kotlin equivalent of Java's String[]?
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 MoreHow does the reified keyword work in Kotlin?
"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 MoreWhat is the Kotlin double-bang (!!) operator?
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 MoreDifference between List and Array types in Kotlin
List and array are two popular collections supported by Kotlin. By definition, both these collections allocate sequential memory location. In this article, we will take an example to demonstrate the difference between these two types of collections.AttributeArrayListImplementationArray is implemented using Array classList or MutableList interfaces are used to implement a List in KotlinMutableArray is mutable, i.e., the values can be changed.List is immutable in nature. In order to create a mutable list, MutableList interface needs to be used.SizeArray is of fixed size. It cannot increase and decrease in size.MutableList do have 'add' and 'remove' functions in order to increase or ...
Read MoreWhat are constants in Kotlin and how to create them?
In every programming language, we need some variable whose value will never change thoroughout the program. In Kotlin too, we have a keyword to create such a variable whose value will remain as constant throughout the program. In order to declare a value as constant, we can use the "const" keyword at the beginning. In this article, we will learn how we can declare a variable as constant in a different way.Example: Top level declarationExampleKotlin const variable can be declared at the top of the programming language and it can be used throughout the file scope.private const val My_TOP_LEVEL_CONST_VAL = ...
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