I am new to Java, so I am not aware of the nitty gritties. Why can't I create generic array of parametrized ArrayList? Instead I have to write, ArrayList<String>[] alist = new ArrayList[10]; or I have to create List of ArrayLists. Aren't arrays supposed to be more efficient than ArrayLists? Then why doesn't Java allow it? Also, what is the difference between following two lines. ArrayList<String>[] alist = new ArrayList[10]; ArrayList<String>[] alist = new ArrayList<?>[10];