How to add one arraylist to other arraylist in android?

Question

I have created 3 arraylists and stored data in it. I need to pass one single arraydata to other page and so I have added my individual arrays to the main array. But when I added one array to other the data is not being aded to that array. Here is my code:

static ArrayList<ArrayList<String>> stringList1=new ArrayList<ArrayList<String>>();
static ArrayList<ArrayList<String>> stringList3; 

stringList1 = Mypage.stringList1;

 ArrayList<String> optionlist = new ArrayList<String>();
stringList3 = new ArrayList<ArrayList<String>>();stringList3 = dbAdapter.selectRecordsFromDBList(query2, null); 
 for (int i = 0; i < stringList3.size(); i++) {
    optionlist = stringList3.get(i);
    System.out.print("option list size");
    System.out.print(optionlist.size());
    stringList1.add(optionlist);
    System.out.println("total stringlist1"+stringList1.get(0));

I am getting the stringList1 array values from Mypage and accessing that in new page. In the new page I am trying to add the optionlist array to stringList1 by giving stringList1.add(optionlist) but the data is not adding. Where I went wrong? Please help me regarding this... Thanks in Advance

Answer 1

Use addAll() It appends all of the elements in the specified ArrayList to the end of this list, in the order that they are returned by the specified Collection's Iterator.

use stringList1.addAll(optionlist); instead of stringList1.add(optionlist);

Answer 2

After seeing your code I can guess that you have problem that elements of arrayList is not copy in another arrayList.If this is your issue then change your code like below

static ArrayList<ArrayList<String>> stringList1=new ArrayList<ArrayList<String>>();
static ArrayList<ArrayList<String>> stringList3; 

stringList1 = Mypage.stringList1;

ArrayList<String> optionlist;
stringList3 = new ArrayList<ArrayList<String>>();
stringList3 = dbAdapter.selectRecordsFromDBList(query2, null); 

 for (int i = 0; i < stringList3.size(); i++) {
    optionlist = new ArrayList<String>();
    optionlist = stringList3.get(i);
    System.out.print("option list size");
    System.out.print(optionlist.size());
    stringList1.add(optionlist);
    System.out.println("total stringlist1"+stringList1.get(0));
 }