Are there any efficient 2D ArrayList classes for Java?

Question

I know that it's possible to create a 2D ArrayList with ArrayList<ArrayList<E>>, but that is cumbersome and a real casting nightmare when it comes to adding and retrieving objects.

Are there any 2D ArrayList classes that do this sort of thing more efficiently? I am writing a true 2D ArrayList class from the ground up, and I'm wondering if there is anyone else who has done this sort of thing in an efficient manner.

Answer 1

no, unfortunately there isn't 2d ArrayList class. your alternative options are (in case 0/1/2 of the Diamension is constant):

MyType[][] myList = new MyType[n][m];

or

ArrayList<MyType>[] myList = new ArrayList<MyType>[n];

or

ArrayList<ArrayList<MyType>> myList = new ArrayList<ArrayList<MyType>>();

another option is to save all your data in 1d ArrayList and create a function that recieve (x,y) and return the place x in the ArrayList. this way you demonstrate outside a 2d array, but save the elements easily in 1d ArrayList

Answer 2

Using the "ArrayList>" type approach is fine and pretty standard for this kind of thing from what I have seen. You can easily write a 2D array list class that provides convenience methods for adding / removing items, etc, and it will be far from "cumbersome" or "a casting nightmare" to use this. Have a look at this implementation as an example. It is not quite perfect but it illustrates how easy it is to use this kind of approach.