Computer scienceProgramming languagesKotlinConcurrency and parallelismParallelismBasics of threads

Thread management

Theory

Calculate the number of distinct characters

Report a typo

Below is the code that reads a string from the standard input and calculates the number of distinct characters in the string. For some reason, the developer Rebecca decided to perform calculations in a new thread. Sadly, her solution doesn't work correctly. Try to fix it.

Additional explanations: the implemented class SlowStringProcessor extends Thread and overrides the method run(). It calculates the number of distinct characters passed to the constructor. The class has a field NumberOfUniqueCharacters that contains the calculated number or 0 if the thread has not calculated the number yet. Keep in mind that SlowStringProcessor works quite slow.

Sample Input 1: 

multithreading

Sample Output 1: 

12
Write a program in Kotlin
// Fix this function
fun main() {
val str: String = readLine()!!
val processor = SlowStringProcessor(str)
println(processor.numberOfUniqueCharacters)
}

// do not change the code below

val mainThreadId = Thread.currentThread().id

class SlowStringProcessor(val s: String) : Thread() {
@Volatile
var numberOfUniqueCharacters: Int = 0
private set

override fun run() {
val currentId = currentThread().id
if (currentId == mainThreadId) {
throw RuntimeException("You must start a new thread!")
}
try {
sleep(2000)
} catch (e: Exception) {
throw RuntimeException("Do not interrupt the processor", e)
}
numberOfUniqueCharacters = s.split("").filter { it != "" }.toTypedArray().distinct().size
}
}
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