Java - Distinct List of Objects

Question

I have a list/collection of objects that may or may not have the same property values. What\'s the easiest way to get a distinct list of the objects with equal properties? I

Answer 1

The ordinary way of doing this would be to convert to a Set, then back to a List. But you can get fancy with Functional Java. If you liked Lamdaj, you'll love FJ.

recipients = recipients
             .sort(recipientOrd)
             .group(recipientOrd.equal())
             .map(List.head_());

You'll need to have defined an ordering for recipients, recipientOrd. Something like:

Ord recipientOrd = ord(new F2() {
  public Ordering f(Recipient r1, Recipient r2) {
    return stringOrd.compare(r1.getEmailAddress(), r2.getEmailAddress());
  }
});

Works even if you don't have control of equals() and hashCode() on the Recipient class.