Sorting an ArrayList of objects using a custom sorting order

Question

I am looking to implement a sort feature for my address book application.

I want to sort an ArrayList contactArray. Contact

Answer 1

This page tells you all you need to know about sorting collections, such as ArrayList.

Basically you need to

• make your Contact class implement the Comparable interface by
  • creating a method public int compareTo(Contact anotherContact) within it.
• Once you do this, you can just call Collections.sort(myContactList);,
  • where myContactList is ArrayList (or any other collection of Contact).

There's another way as well, involving creating a Comparator class, and you can read about that from the linked page as well.

Example:

public class Contact implements Comparable {

    ....

    //return -1 for less than, 0 for equals, and 1 for more than
    public compareTo(Contact anotherContact) {
        int result = 0;
        result = getName().compareTo(anotherContact.getName());
        if (result != 0)
        {
            return result;
        }
        result = getNunmber().compareTo(anotherContact.getNumber());
        if (result != 0)
        {
            return result;
        }
        ...
    }
}