Java 2D ArrayList and sorting

Question

I need to sort a shopping list by the aisle the item is located for example:
[Bread] [1]
[Milk] [2]
[Cereal] [3]

I am planning to do this with ArrayList and

Answer 1

Don't you have a class that holds your item + aisle information? Something like:

public class Item {
  private String name;
  private int aisle;

  // constructor + getters + setters 
}

If you don't, consider making one - it's definitely a better approach than trying to stick those attributes into ArrayList within another ArrayList. Once you do have said class, you'll either need to write a Comparator for your objects or make 'Item' Comparable by itself:

public class Item implements Comparable {
  .. same stuff as above...

  public int compareTo(Item other) {
    return this.getAisle() - other.getAisle();
  }
}

Then all you do is invoke sort:

List items = new ArrayList();
... populate the list ...
Collections.sort(items);