ArrayList object sorting

Question

Hi, I have to sort ArrayList which consists of objects. Object: ID, Quantity. The ArrayList should be sorted by ID. How to implement this?

ItemIdQuantity = new ItemIdQuantity (ID, Quantity);

ItemIdQuantity.Sort(); // where must be sorting by ID

Answer 1

public class IdComparer : IComparer  {
  int IComparer.Compare(object x, object y) {
      return Compare((ItemIdQuantity)x, (ItemIdQuantity)y);
  }
  public int Compare(ItemIdQuantity x, ItemIdQuantity y) {
      return x.ID - y.ID;
  }
}

arrayList.Sort(new IdComparer());

Answer 2

Assuming that this is Java:

• If the ItemIdQuantity class implements Comparable based on the ID field, use Collections.sort() with the list as single parameter.
• Otherwise, implement a Comparator that compares the objects using their ID, and use it as second paramter to Collections.sort().