arraylist of arraylist
public static void main(String[] args) { ArrayList<ArrayList<Integer>> outer = new ArrayList<ArrayList<Integer>>(); ArrayList<Integer> inner = new ArrayList<Integer>(); inner.add(100); inner.add(200); outer.add(inner); // add first list inner = new ArrayList<Integer>(inner); // create a new inner list that has the same content as // the original inner list outer.add(inner); // add second list outer.get(0).add(300); // changes only the first inner list System.out.println(outer); }
