Adding several ArrayList elements into one ArrayList

Question

I have several "ArrayList"

Like this:

ArrayList<Integer> list1;
ArrayList<Integer> list2;
ArrayList<Integer> list3;




  list1: [0,1,2]
  list2: [22,12,23,24,53]
  list3: [21,43,21,7]

I want to put all elements of all lists into one ArrayList like

sumList [0,1,2,22,12,23,24,53,21,43,21,7]

How is that to be done?

thx u

[Research effort helps sometimes](http://docs.oracle.com/javase/7/docs/api/java/util/List.html#addAll%28java.util.Collection%29). — Tom, Dec 09 '14 at 15:15

score 2 · Accepted Answer · answered Dec 09 '14 at 15:15

2

Use addAll :

ArrayList<Integer> list = new ArrayList<Integer>(list1);
list.addAll(list2);
list.addAll(list3);

answered Dec 09 '14 at 15:15

Eran

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score 1 · Answer 2 · answered Dec 09 '14 at 15:22

1

if you want to have a single toolkit method:

public static <T> List<T> merge(List<T>...args) {
    List<T> list = new ArrayList<T>(args[0]);
    for (int i = 1; i < args.length; i++)
        list.addAll(args[i]);
    return list;
}

answered Dec 09 '14 at 15:22

stealthjong

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score 0 · Answer 3 · answered Dec 09 '14 at 15:16

0

list1.addAll(list2);
list1.addAll(list2);

answered Dec 09 '14 at 15:16

Nasir

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Adding several ArrayList elements into one ArrayList

3 Answers3