Concurrency and parallelism

Multithreading is based on the concepts of concurrency and parallelism. Concurrency refers to the ability of a task to be split into independent subtasks that can be executed out of order without affecting the final result:

Let's look at the following example:

class Baker {
    fun bake(): Cake {
        for (i in 0..1_000_000_000) {
            BigInteger.ONE.modPow(BigInteger.TEN, BigInteger.TEN)
        }
        return Cake()
    }
}

The Baker class contains the bake() method, which invokes the modPow function that take a significant amount of time to imitate the process of baking and returns an instance of the Cake class:

class Cake

The Bakery class contains the order method, which takes the numberOfCakes argument and returns an instance of the List<Cake> type:

class Bakery {
    fun order(numberOfCakes: Int): List<Cake> {
        val cakes = mutableListOf<Cake>()
        val baker = Baker()
        val bakingTask = Runnable {
            cakes...