Comment¶

HashTable is a trait without a factory method and thus cannot be instantiated. HashMap and HashSet are subclasses that you should use.

https://stackoverflow.com/questions/3648870/scala-using-hashmap-with-a-default-value

1. Avoid using assert in Java production code as assertion is not turned on by default. Throw exception instead (since assert is just a syntax sugar of throwing exceptions).

The most important thing to remember about assertions is that they can be disabled, so never assume they'll be executed.

Therefore keep the followings things in mind when using assertions:

MutableList vs ArrayList¶

MutableList is ArrayList in Kotlin currently.

Create an Empty MutableList¶

Below is the most idiomatical way to create an empty mutable list in Kotlin.