How to declare an ArrayList

[albert kao]

Which of the following two definitions is better?
Is there a better way than the following two definitions?

List<ArrayList<Integer>> data = new ArrayList<ArrayList<Integer>>(); 
       for(int i = 0; i < 5; ++i) {
        	ArrayList<Integer> column = new ArrayList<Integer>();
            data.add(column);
        }

ArrayList<ArrayList<Integer>> data = new ArrayList<ArrayList<Integer>>(); 
        for(int i = 0; i < 5; ++i) {
        	ArrayList<Integer> column = new ArrayList<Integer>();
            data.add(column);
        }

[Campbell Ritchie]

Please don’t add a new question to an old post. Fortunately I can split your question into a new thread.
They are both poor forms. The correct way to do it in Java7 is

List<List<Integer>> data = new ArrayList<>(5);

In older versions of Java you would write

List<List<Integer>> data = new ArrayList<List<Integer>>(5);

The reason is that the declaration does not commit you to using an ArrayList; you could use a LinkedList or other sort of List anywhere. Your outer List could even contain several different List implementations, but they would all contain Integers.
You should only use the constructor argument 5 if you are sure you will be using 5 elements.

[Campbell Ritchie]

You can use different kinds of List; you might reassign the reference like this

// Only works if data was declared as a List
data = new LinkedList<List<Integer>>();