Java question about ArrayList<Integer>[] x

Question

I have always had this one issue with arrays of ArrayLists. Maybe you can help.

//declare in class
private ArrayList<Integer>[] x;

//in constructor
x=new ArrayList[n];

This generates a warning about unchecked conversion.

But

x=new ArrayList<Integer>[n];

is a compiler error.

Any idea?

Thanks!

Answer 1

I think you cannot make array of generic arraylist because no generic information will be available at runtime.Instead you can do like this:

List<Integer>[] arr=new ArrayList[30];
arr[0]=new ArrayList<Integer>();//create new arraylist for every index.

Answer 2

You can't make a array of generics lists. Fortunately, there are workarounds. And even more fortunately, there is a nice site about Generics with more information than you'd ever want to know. The link goes straight to the Arrays in Java Generics part.