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I am trying to initialise a list with a size in the constructor. But the size of my list is 0.

val seqList = ArrayList<ArrayList<Int>>(N) // This has the Problem
val queries = ArrayList<Query>(Q) // This works like a charm

I have both N and Q set as non zero inputs from the user lets say N = 100 and Q = 100

While debugging my code I found out that, queries.size() = 100 but seqList.size() = 0

Is my assumption incorrect, that seqList should also have been initialized with N ArrayList<Int> objects.

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    Are you sure that queries.size() is non zero? That constructor sets the capacity, not the size. Commented Aug 13, 2017 at 14:58
  • I was putting the breakpoint at the wrong point, you are right. The constructor does not set the size, but the capacity :) Commented Aug 13, 2017 at 15:29

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Your assumption isn't correct, I'm afraid.

Quoted from the documentation of ArrayList:

Provides a MutableList implementation, which uses a resizable array as its backing storage.

This implementation doesn't provide a way to manage capacity, as backing JS array is resizeable itself. There is no speed advantage to pre-allocating array sizes in JavaScript, so this implementation does not include any of the capacity and "growth increment" concepts.

The constructor particularly:

ArrayList(initialCapacity = 0))

Creates an empty ArrayList.

An empty ArrayList is created, thus providing 100 as an argument will not create elements inside the list.

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