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

You might be better of using a map instead of 3 dimension list — Shervin Asgari, Oct 25 '13 at 18:56
@Maxim : Is there a more efficient way I can successfully capture the information I want to in Java? I will need to store it in some form or the other to be able to work on it. — 42cornflakes, Oct 25 '13 at 18:57
Are you sure this is the most effective data structure? Does it make sense for some of these lists to be your own classes? — Zong, Oct 25 '13 at 18:58
@Shervin: Thanks for the suggestion. Could you elaborate on the advantage I might get from that? — 42cornflakes, Oct 25 '13 at 19:01
@Zong: This is the only thing I could think of. I'm welcome to other methods. Just that I might not be aware of it and might need a helping hand understanding it. Or would you suggest creating a class for capturing this and making it cleaner? — 42cornflakes, Oct 25 '13 at 19:03
I'm asking if there is any hierarchy for these lists that make classes make sense. Eg. Top level is countries, inner level is cities, etc. — Zong, Oct 25 '13 at 19:05
Lets call A->B as a dependency with A the determinant and B the dependent. Outer list has the list of all dependencies. Middle list captures the information of a single dependency. The 2 inner lists capture the list of determinants and dependents respectively. — 42cornflakes, Oct 25 '13 at 19:12
Its difficult to say without knowing the complete picture of your objects, but if you can have an object act as a key, then this is much faster, easier and better solution — Shervin Asgari, Oct 25 '13 at 19:20
@Shervin: Unfortunately, the determinant as well as the dependent (elaborated in the previous comment) can have duplication. Hence the predicament. — 42cornflakes, Oct 25 '13 at 19:24
If duplication in the key, you can always use multimap from google guava — Shervin Asgari, Oct 27 '13 at 14:36

score 0 · Accepted Answer · answered Oct 25 '13 at 19:05

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);
    }
}

Thanks a lot. The answer I was looking for. Will keep it open for some time just in case somebody offers alternate design suggestions. — 42cornflakes, Oct 25 '13 at 19:22

bstempi · Answer 2 · 2013-10-25T19:41:38.903

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));

Adding values to 3 dimensional list in Java

2 Answers2