Why does list insertion fail when sufficient size is provided on construction?

Question

If we have the following variable declaration:

List list = new List(5);

Why does this:

list.insert(2, 3);


        

Answer 1

The initial size is used to indicate the size of the internal array, initially.

When you insert items into a List, it stores them in an array. When the array is full, it creates a new array of double the size, and copies all of the items. If you have an idea that you are going to be putting in 5000 items, you would want to specify that hint so it doesn't end up doing a lot of array resizing / copying.

The initial size does not indicate that there are any items in the list though.

Answer 2

That is because the integer you specify in the constructor is the amount that the List can hold. When items are added, the list is automatically increased. The resizing is avoided when you specify an initial capacity that matches the number of items that you want to add.

However, you still have to use the Add method to add new items.

See the remarks section in the documentation