Adding values to 3 dimensional list in Java

Question

Short Version

How do you add values to a 3 dimensional array list at one go?

List<List<List<String>>> FD = new ArrayList<List<List<String>>>();

I learnt that for a normal Arraylist, the following can be done

List<String> R = new ArrayList<String>();
R.addAll(Arrays.asList("A","B","C","D","E"));

Longer Version

Note: I'll be using '->' symbol to represent 'determines'.
Read A -> B as 'A determines B'.

I am trying to capture the following information in some way.
A -> B, A,B -> C, B -> D,E

I felt a 3D list would come in handy as I pictured it in the following form

F[             --> Outermost List starts
  [            --> Middle List start (first of the three middle lists)
   [A],
   [B]
  ],            --> Middle List end
  [
   [A,B],        --> Innermost list start and end (first of the two inner lists in this middle list)
   [C]
  ],
  [
   [B],
   [D,E]
  ]
 ]             --> Outermost List ends

I chose a List since the size is dynamic to some extent (except that every middle list will always have only 2 inner lists)

I would appreciate if you could show me a simple way of populating such a list.

If you have some alternate implementation suggestions, I'm open to that too.

Thanks in advance

Answer 1

Like this. I copied Lists.newArrayList from Guava library.

import java.util.ArrayList;
import java.util.Collections;

public class Test {
    public static <E> ArrayList<E> newArrayList(E... elements) {
        ArrayList<E> list = new ArrayList<>(elements.length);
        Collections.addAll(list, elements);
        return list;
    }

    public static void main(String[] args) {

        ArrayList<ArrayList<ArrayList<String>>> lists = newArrayList(
            newArrayList(
                newArrayList("A"),
                newArrayList("B")
            ),
            newArrayList(
                newArrayList("A", "B"),
                newArrayList("C")
            ),
            newArrayList(
                newArrayList("B", "D"),
                newArrayList("E")
            )
        );

        System.out.println(lists);
    }
}

Answer 2

This isn't strictly answering your question (the answer doesn't involve lists), but instead an alternate approach. In your question, you have some coordinate to represent each String value. Perhaps using a Map would be best.

Class to define the key:

public class Coordinate {
    private int x, y, z;

    // Static factory to make your code read a little better
    public static Coordinate create(int x, int y, int z) {
        return new Coordinate(x, y, z);
    }

    public Coordinate(int x, int y, int z) {
        // set this.x, this.y, this.z
    }

    public boolean equals(Object o) {
        // Compare this.x, y, z with o.x, y, z
    }

    public int hashCode() {
        // I'm sure you can come up with something
    }
}

Now, you could do something like this:

Map<Coordinate, String> map = new HashMap<Coordinate, String>();
map.put(Coordinate.create(1, 2, 3), "Some value");

// Prints out "Some value"
System.out.println(map.get(Coordinate.create(1, 2, 3));