javaType

Returns a Java Type instance corresponding to the given Kotlin type.

@ExperimentalStdlibApival KType.javaType: Type(source)

import kotlin.reflect.*
import kotlin.reflect.full.starProjectedType
import java.lang.reflect.Type

@OptIn(ExperimentalStdlibApi::class)
fun main() {
    // Kotlin type for String
    val kotlinType: KType = String::class.starProjectedType

    // Corresponding Java Type
    val javaType: Type = kotlinType.javaType

    println(javaType.typeName)   // prints "java.lang.String"
}

Source