How to create objects dynamically during runtime Java

Question

I'm trying to make a program that is going to need to dynamically create ArrayLists along the lines of this:

for (int i = 0; i < arbitraryInt; i++){
    //code to make 5 new arraylists
}

However I can't seem to find any method that would accomplish this.

Edit: I am trying to make a columnar cipher for my APCS class. This cipher requires me to convert a string of any length into a grid. In this case each arraylist would be a column. So to be more specific my code would look somewhat like this:

String encode = "somethingsomethingyadayadayada";
int x = 0, y = 0;

for (int i = 0; (i*i) < encode.length(); i++){
    y = i;
    x = i-1;
}
for (int i = 0; i < x; i++){
    //make an arraylist
}

Is this better @Kartic? I tried to keep it non specific as to keep my post from becoming a code dump.

Well, where do you want to put them? What do you want to do with them? — Louis Wasserman
– Louis Wasserman, Commented Nov 8, 2018 at 2:36
what's wrong with using new ArrayList() 5 times, or in a loop? or having List<List<Integer>>? — Kartik
– Kartik, Commented Nov 8, 2018 at 2:38
In the final version of what I'm trying to make, the number of arraylists will vary depending certain parameters. — Sumtinlazy
– Sumtinlazy, Commented Nov 8, 2018 at 2:40
@Sumtinlazy what parameters? please complete your question.. "along the lines of this" is not enough — Kartik
– Kartik, Commented Nov 8, 2018 at 2:44

uli · Accepted Answer · 2018-11-08 02:37:39Z

1

One of the possible solution is to store lists inside list:

List<List<Integer>> listOfLists = new ArrayList<>();
for (int i = 0; i < arbitraryInt; i++){
    listOfLists.add(new ArrayList<>());
}
// get third list
List<Integer> third = listOfLists.get(2);

answered Nov 8, 2018 at 2:37

uli

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