Deleting Data Objects -> Asynchronous API sample code -> remove()'s second argument’s type is incorrect.
-> http://backendless.com/documentation/data/android/data_deleting_data_objects.htm
Backendless.Persistence.of( Contact.class ).remove( savedContact, new AsyncCallback<Contact>()
==>
Backendless.Persistence.of( Contact.class ).remove( savedContact, new AsyncCallback<Long>()