Adding ArrayList to ArrayListArrayList

Question

Suppose we have an ArrayListArrayList(String)

[[a,b,c,d] , [e,f,g,h]]

and an ArrayList(String)

[1,2,3]

How can we add ArrayList to ArrayListArrayList in position 1 at the end in order to get

[[a,b,c,d] , [e,f,g,h,1,2,3]]

Thanks

Answer 1

I think you need a add(int, E) method

List<ArrayList<String>> dataHolder = new ArrayList<ArrayList<String>>();

List<String> firstData = new ArrayList<String>();
firstData.add("a");
firstData.add("b");
firstData.add("c");
firstData.add("d");

List<String> secondData = new ArrayList<String>();
secondData.add("e");
secondData.add("f");
secondData.add("g");
secondData.add("h");
secondData.add("1");
secondData.add("2");
secondData.add("3");

dataHolder.add(secondData);
dataHolder.add(0, firstData); // insert your List<String> to 0 index position in dataHolder

Answer 2

If we name your ArrayList<ArrayList> m and if we name your ArrayList a, then you could use

m.get(1).addAll(a)

Description for this method provided by Oracle here: http://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html

Answer 3

//pseudocode
List<ArrayList<String>> arraylistarraylist = [[a, b, c, d], [e, f, g, h]];    

List<String> list = Arrays.asList(1,2,3);

arraylistarraylist.get(1).addAll(list);