Updated July 5, 2023
Introduction to Kotlin kclass
The kotlin kclass is one of the types it comes under a language like java.lang package, and it is mainly used to hold the references for the kotlin classes. Using these classes, the reflection concept will play a wide role, and using the type parameter of the specified classes like kClass, it can be referred to by using the references so that kclass is referred to as the counterpart of the lang package. It can also be enumerated and access all the method declarations containing child and parent classes. We get the instance of the KClass by calling class name:: class model.
Syntax
In kotlin, language class is the most important part of implementing the application, and we call its methods and attributes on any application area. We can use many api that regarding and represent the classes. That KClass is one type that can act as the datatype.
class name
{
val variablename= name();
val varname= variablename.javaClass.kotlin
-----some logics depends on the requirement—
}
interface kclass<>{
val vars:String // any datatype
-------some declaration codes ---
}The above codes are the basic syntax for utilizing the kclass on both class and interface. We can declare the variable with specific data types, which can be called through the kclass type.
How does kclass Work in Kotlin?
Generally, the kotlin class works with many scenarios to implement the application. We can use many methods to execute the user operations, and it can be called upon the main method with the help of the class object. The mapping and serialization of the kClass type include its superclasses and interfaces, creating a corresponding counterpart for the Java lang package. It is of any type related to the class, and while creating the object of the class, it holds the reference for each kotlin class. It empowers you to carry out operations on those classes from the perspective of reflection, and the type parameter of the kClass determines which Kotlin classes can be referenced by any of the references.
We used the Java method to get the class instance and converted it to a kClass routine using the Class.forName method. We also pass the parameters of the class and the list type. It does not include the type parameters of both the inner and outer classes. The parameter arguments are like the KTypeParameters, which can pass to abstract and non-abstract classes and methods. We also classified the classes on the KClass type at the runtime from the JVM(java virtual machine).
Examples of Kotlin kclass
Let us discuss examples of Kotlin kclass.
Example #1
Code:
package one
import java.io.Serializable
import kotlin.reflect.full.superclasses
class Test:Serializable{
}
fun main(args: Array<String>) {
val eg = Test::class
println(eg.superclasses)
val p: Int = 54
val q: Int = 76
val sum = p + q
println("The total sum is: $sum")
val r = listOf("jan", "feb", "mar", "apr", "may", "jun", "jul", "aug", "sep", "oct")
val s = r.groupingBy { it.first() }
.fold({ key, _ -> key to mutableListOf<String>() },
{ _, accumulator, element ->
accumulator.also { (_, list) -> if (element.length % 2 == 0) list.add(element) }
})
val t = s.values.sortedBy { it.first }
println(t)
val v = listOf("jan", "feb", "mar", "apr", "may", "jun", "jul", "aug", "sep", "oct")
val u = r.groupingBy { it.first() }
.fold(listOf<String>()) { acc, e -> if (e.length % 2 == 0) acc + e else acc }
println(u)
val fd = listOf(32, 35, 73, 12, 17, 212, 31, 53, 84)
val rf = fd.reduce { rf, vars -> rf + vars }
val mp = HashMap<Int, String>()
mp.put(1, "siva")
mp.put(2, "raman")
mp.put(3, "welcome")
mp.put(4, "users")
mp.put(5, "have")
mp.put(6, "a")
mp.put(7, "nice")
mp.put(8, "day")
val akeys = ArrayList(mp.keys)
val avalues = ArrayList(mp.values)
println("Your input keys are : $akeys")
println("Your input values are: $avalues")
val y = listOf("mar", "apr", "may", "jun", "jan", "jul", "aug", "sep", "oct")
val out= y.reduceRight{ news, eg -> "$eg-$news" }
println(out)
}Output:
In the above example, we used KClasses with collection concepts like hashmap to store the data using the key-value pairs.
Example #2
Code:
package one
import java.lang.reflect.*
import kotlin.reflect.KClass
import kotlin.reflect.KType
import kotlin.reflect.KTypeProjection
import kotlin.reflect.KVariance
import kotlin.reflect.full.createType
inline fun <reified T : Any> getKType(): KType =
object : demos<T>() {}.first()
@Suppress("unused")
open class demos<T>
fun demos<*>.first(): KType =
javaClass.genericSuperclass.toKType().arguments.single().type!!
fun KClass<*>.toInvariantFlexibleProjection(arguments: List<KTypeProjection> = emptyList()): KTypeProjection {
val eg = if (java.isArray()) listOf(java.componentType.kotlin.toInvariantFlexibleProjection()) else arguments
return KTypeProjection.invariant(createType(eg, nullable = false))
}
fun Type.toKTypeProjection(): KTypeProjection = when (this) {
is Class<*> -> this.kotlin.toInvariantFlexibleProjection()
is ParameterizedType -> {
val p = (rawType as Class<*>).kotlin
p.toInvariantFlexibleProjection((p.typeParameters.zip(actualTypeArguments).map { (parameter, argument) ->
val projection = argument.toKTypeProjection()
projection.takeIf {
parameter.variance == KVariance.INVARIANT || parameter.variance != projection.variance
} ?: KTypeProjection.invariant(projection.type!!)
}))
}
is WildcardType -> when {
lowerBounds.isNotEmpty() -> KTypeProjection.contravariant(lowerBounds.single().toKType())
upperBounds.isNotEmpty() -> KTypeProjection.covariant(upperBounds.single().toKType())
else -> KTypeProjection.STAR
}
is TypeVariable<*> -> TODO()
else -> throw IllegalArgumentException("Thank you users It is a Unsupported format type: $this")
}
fun Type.toKType(): KType = toKTypeProjection().type!!
fun main(eg: Array<String>) {
println(getKType<List<Map<String, Array<Double>>>>())
println("Welcome To My Domain its a second example regarding the kotlin kclass type")
println(getKType<Array<*>>())
}Output:
In the second example, we used KType and its methods which help to utilize and override the KClasses.
Example #3
Code:
package one;
import java.io.Serializable
import kotlin.reflect.full.superclasses
class Third:Serializable{
fun eg1() {
println("Its a first method")
}
fun eg2() {
println("Its a second method")
}
fun eg3() {
println("Its a third method")
}
}
abstract class sample{
abstract fun eg4()
abstract fun eg5()
}
class new1 : sample() {
override fun eg4(){
val m=12
println(m)
}
override fun eg5(){
println("Its a second method which inherits from the new class")
}
}
fun main(args: Array<String>) {
val eg = Third::class
println(eg.superclasses)
val eg1= new1::class
println(eg1.superclasses)
}Output:
In the final example, we used the abstract class concepts to implement the application, additionally using KClasses.
Conclusion
In Kotlin language, we used a lot of default classes and methods to implement the application with overcome from the Java-based applications and its tasks. That KClass is one of the types for storing the reference of the classes and its methods for overriding and overwriting the methods required by the programmer.
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