Convert List of List into list in java

Question

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

List<String> list1 = new ArrayList<String>();
list1.add("a1");
list1.add("a2");

List<String> list2 = new ArrayList<String>();
list2.add("b1");
list2.add("b2");

List<String> list3= new ArrayList<String>();
list3.add("c1");
list3.add("c2");

superlist.add(list1);
superlist.add(list2);
superlist.add(list3);

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

Now I want to create a new list which contains all the values in superList. Here result should contain a1,a2,b1,b2,c1,c2

Answer 1

Try like this using flatMap:

List<List<Object>> list = 
List<Object> lst = list.stream()
        .flatMap(Collection::stream)
        .collect(Collectors.toList());