2D ArrayList, add an ArrayList to another

Question

So I'm trying to create a 2d ArrayList but I'm having some trouble adding one list to another. I found this question that seemed to answer my question but when I try it out myself I get a red warning squiggle under the last add on coordinates.add()

Here's my code

ArrayList<String> coordinates = new ArrayList<String>();
ArrayList<String> buffer = new ArrayList<String>();
buffer.add("123");
buffer.add("abc");

coordinates.add(buffer);

What am I doing wrong here?

If you're using at least Java 7, be sure to use the [diamond operator `<>`](http://stackoverflow.com/q/4166966/5743988) — 4castle, Sep 04 '16 at 05:41

score 2 · Answer 1 · answered Sep 04 '16 at 05:40

2

you created two arraylist of string name coordinates and buffer. so you can not add one arraylist into a arraylist of string . if you want to add a array list into another then try following code

   ArrayList<ArrayList<String>> coordinates = new ArrayList<ArrayList<String>>();
  ArrayList<String> buffer = new ArrayList<String>();
  buffer.add("123");
  buffer.add("abc");

  coordinates.add(buffer);

answered Sep 04 '16 at 05:40

Abhishek

379
1
8

Im tired and its late, I had it set to ArrayList>and I must of changed it and forgot to put it back.. thanks man – Yitzak Hernandez Sep 04 '16 at 06:06

score 0 · Answer 2 · answered Sep 04 '16 at 05:40

0

coordinates should be of type ArrayList<ArrayList<String>>

ArrayList<ArrayList<String>> coordinates = new ArrayList<ArrayList<String>>();

answered Sep 04 '16 at 05:40

Guy

46,488
10
44
88

yux0210 · Answer 3 · 2016-09-04T05:59:16.833

0

like this : coordinates.addAll(buffer);

edited Sep 04 '16 at 05:59

answered Sep 04 '16 at 05:53

yux0210

1
2

Please add description and more detail to the answer just for helps more – Hossein Sep 04 '16 at 06:07

score 0 · Answer 4 · answered Sep 04 '16 at 06:12

Just use addAll method Instead of using add like below:

ArrayList<String> coordinates = new ArrayList<String>();
ArrayList<String> buffer = new ArrayList<String>();
buffer.add("123");
buffer.add("abc");

coordinates.addAll(buffer);

it will not give any error or warning.. thank you..

2D ArrayList, add an ArrayList to another

4 Answers4