How to initialize List Of List in one line

Question

How can I initialize a List Of Lists in one line?

List<List<Integer>> list = .....;

There's a very complete answer over here already: https://stackoverflow.com/a/47288158/236528 — mjuarez, Nov 13 '18 at 21:26

Malt · Accepted Answer · 2021-08-17T19:59:24.047

26

List<List<Integer>> list = Arrays.asList(Arrays.asList(1,2), Arrays.asList(3,4));

In Java 9+ you can replace Arrays.asList() with List.of():

List<List<Integer>> list = List.of(List.of(1,2), List.of(3,4));

edited Aug 17 '21 at 19:59

answered Nov 13 '18 at 22:03

Malt

Liad Saubron · Answer 2 · 2018-11-14T08:09:17.730

1

List<List<Integer>> list = 
    Arrays.asList(Arrays.asList(1,2,3), Arrays.asList(4,5,6));

edited Nov 14 '18 at 08:09

answered Nov 13 '18 at 21:29

Liad Saubron

Why so defensive? – shmosel Nov 13 '18 at 21:37
@shmosel what do you mean? – Liad Saubron Nov 13 '18 at 21:39
2

Why do you need to copy it to a `new ArrayList`? – shmosel Nov 13 '18 at 21:42
edited, thanks! @shmosel – Liad Saubron Nov 14 '18 at 08:09

2 Answers2