Initial size for the ArrayList

The initial size of an ArrayList in Java is 0. The ArrayList class is a resizable array implementation of the List interface, which means that the size of the ArrayList can grow or shrink as needed to accommodate the elements added to or removed from the list.

By default, the ArrayList class creates an empty list with an initial capacity of 10. This means that the ArrayList will automatically resize itself when you add the eleventh element to the list, and it will allocate a new array with a capacity of 20 to store the elements.

You can specify a different initial capacity for the ArrayList when you create it, using the ArrayList(int initialCapacity) constructor.

For example:

List<String> list = new ArrayList<>(20);

This will create an ArrayList with an initial capacity of 20. The ArrayList will still resize itself as needed when you add more elements to the list, but it will not need to do so as often as it would with the default initial capacity of 10.

Keep in mind that specifying a larger initial capacity will increase the amount of memory used by the ArrayList, but it can improve the performance of the ArrayList if you know that you will be adding a large number of elements to the list.

I hope this helps! Let me know if you have any other questions.