Java 8 Lambda: Comparator

Question

I want to sort a list with Lambda:

List messagesByDeviceType = new ArrayList();      
messagesByDeviceType.sort((Message o1, Messag         


        

Answer 1

The Comparator's compare() method must return an int, and it seems yours is returning a long.

You can change it to:

(Message o1, Message o2)->Long.compare(o1.getTime(),o2.getTime())

This is assuming (based on your error message) that o1.getTime() returns a long.