How to create a HashMap with ArrayList<ArrayList<Integer>>

Question

I am trying to create a HashMap which will look like this

key.   value
1.     [[1,2,5][4,5]]
2.     [[12,2][45,54]]
3.     [[1,23][43,25]]

I get these values from the user as a ArrayList. How do I add the values to the map

i declared tha map as

HashMap<Integer,ArrayList<ArrayList<Integer>>> map = new HashMap<>();

I tried to insert the value like

map.put(i,new ArrayList<ArrayList<Integer>>>(userInput));

but I get a error since userInput is just ArrayList

What do you mean by, "userInput is just ArrayList"? Can you show the declaration of userInput? — MaxG
– MaxG, Commented Sep 28, 2021 at 23:43

MaxG · Accepted Answer · 2021-09-28 23:45:24Z

2

This works when working with java 11:

import java.util.*;

public class MyClass {
    public static void main(String args[]) {
      List<Integer> inner = List.of(1, 2, 3, 4);
      List<List<Integer>> outer = List.of(inner, inner);
      
      Map<Integer, List<List<Integer>>> map = Map.of(5, outer);
      
      System.out.println(map); // {5=[[1, 2, 3, 4], [1, 2, 3, 4]]}
    }
}

answered Sep 28, 2021 at 23:45

MaxG

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2 Comments

user10183910 Over a year ago

how do I add a new value to the map, Ex :{5=[[1, 2, 3, 4], [1, 2, 3, 4],[4,3,5]]}

MaxG Over a year ago

using put the same way

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