Make array from a list and initialize it - Java

Question

I have the following lists in a class

List<XYZ> Algo1;
List<XYZ> Algo2;
List<XYZ> Algo3;

and what I want is to create an array with these lists, try to do it like this:

List<XYZ> Algos[] = {Algo1,Algo2,Algo2};

I would like to be able to initialize it like that, but I get an error, the idea is to be able to call by means of a for and not individually

for(int i=0;i<Algos.length;i++){
    Algos[i].add(new XYZ(...));
}

Something like that, some idea?

@Sweeper porq that solution does not satiface completely the question, it must be with an array of type List <XYZ>, unless you say that this is not possible — Samir Llorente
– Samir Llorente, Commented Apr 3, 2018 at 2:09
@SamirLlorente it is impossible. Did you look at the link? It explains this very well. — Sweeper
– Sweeper, Commented Apr 3, 2018 at 6:18

Sweeper · Accepted Answer · 2018-03-30 10:09:42Z

3

See the link for why.

Anyway, an alternative to this is to create a List<List<XYZ>>:

List<List<XYZ>> algoList = Arrays.asList(algo1, algo2, algo3);

Btw, remember to properly initialise algo 1-3 before putting them in a list! Otherwise you'll be putting nulls into a list!

If you want to add/remove stuff from algoList, you need an ArrayList<List<Algo>>:

ArrayList<List<XYZ>> algoList = new ArrayList<>(Arrays.asList(algo1, algo2, algo3));

answered Mar 30, 2018 at 10:05

Sweeper

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3 Comments

you might also want to suggest new ArrayList<>(Arrays.asList(algo1, algo2, algo3)) if the OP wants the algoList to be mutable.

@Aominè Seeing how OP tried to create an array of lists, I assumed that OP does not intend to add/remove stuff, but good point anyway!

Instead of using another list, can not it be with an array?