Question

I have a condition like this

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

    for(int i=0; i<3; i++){
      mainList = getList();
    }

private static List<String> getList() {
    List<String> listName = new ArrayList<String>();
    listName.add("String");
    return listName;
  }

As mainList is getting List<String> in return and mainList itself a list of Strings. How can I keep updating mainList with those strings in listName returning from method.

If you give any solution will that also apply on Maps?

Answer 1

To append a list to an existing list use the addAll method:

mainList.addAll(getList());

For Map you have putAll:

map1.putAll(map2);