How to sort list of custom integers? Collections.sort()?

Question

I have array of custom integers:

ArrayList<MyCustomInteger> list1 = new ArrayList<MyCustomInteger>

I need integers to be custom since i want them to hold some additional methods. Now this doesn't work for custom:

Collections.sort(list1);

How can I sort them?

Provide a custom comparator to the overloaded sort method? Or make your MyCustomInteger class implement the Comparable interface. — Alexis C., Feb 11 '15 at 21:58
Make sure `MyCustomInteger` implements `Comparable` or provide a custom `Comparator`. — Luiggi Mendoza, Feb 11 '15 at 22:00
Allow your class to implement the comparable interface. Check out this link detailing how to do it! http://www.tutorialspoint.com/java/java_using_comparator.htm — Evan Bechtol, Feb 11 '15 at 22:01
Can't you just have your custom integer inherit from the Integer class, and thus they will be compared the same way in the list when sorting? — Malik Brahimi, Feb 11 '15 at 22:17
@Malik , not sure how to do it - Eclipse throws error: "The type MyCustomInteger cannot subclass the final class Integer" — ShoulO, Feb 11 '15 at 22:44

score 1 · Accepted Answer · edited May 23 '17 at 12:27

1

Your MyCustomInteger class must implement the Comparable interface. Alternatively, you have to pass a Comparator instance to the sort method.

Read these:

edited May 23 '17 at 12:27

Community

answered Feb 11 '15 at 22:00

Wouldn't it be easier to extend the Integer class? – Malik Brahimi Feb 11 '15 at 22:17
Look here: http://docs.oracle.com/javase/7/docs/api/java/lang/Integer.html. The `Integer` class is `final`, you can't extend it. – Francesco Palmiotto Feb 11 '15 at 22:18
Is there a work around to extend it? Like type alias? – Malik Brahimi Feb 11 '15 at 22:20
No, because extending it makes no sense. How can you extend an integer? – Francesco Palmiotto Feb 11 '15 at 22:21
With a wrapper class? See [here](http://stackoverflow.com/questions/2148679/equivalent-to-extending-a-final-class-in-java). – Malik Brahimi Feb 11 '15 at 22:21
I know, but it's quite a mess because you have to create wrappers for all of the methods of the final class you're trying to extend. Definitely not a good solution. – Francesco Palmiotto Feb 11 '15 at 22:25
I implement the Comparable. Thanks 4 second link. – ShoulO Feb 11 '15 at 22:36

1 Answers1