How to fill a List of Lists?

Question

I create a list of lists like this:

List tmp = new ArrayList(2);

Then I\'d like to insert 10 to first sub-list as follo

Answer 1

You have not initialized the inner list. That's the reason you are getting the error.

Following code will initialize each of the inner list.

int initialCapacity=2;
List tmp = new ArrayList(initialCapacity);
for(int i = 0; i < initialCapacity; i++)
     tmp.add(new ArrayList());