SortBy crash violates contract

Question

Hey guys I have this code to compare by duration but I keep getting this error:

Fatal Exception: java.lang.IllegalArgumentException Comparison method violates its general contract!

Here is my code:

Collections.sort(list, new Comparator<MyProduct>() {

    @Override
    public int compare(MyProduct lhs, MyProduct rhs) {
        Integer lDuration = (lhs != null ? lhs.getDuration() :0);
        Integer rDuration = (rhs != null ? rhs.getDuration() :0);

        return lDuration.compareTo(rDuration);
    }
});

What are the durations being compared that lead to the error? — Carcigenicate, Nov 10 '17 at 13:00

score 0 · Answer 1 · answered Nov 10 '17 at 13:24

You are violating the requirements of consistency with equals:

When we say that the ordering imposed by c on S is consistent with equals, we mean that the quotient for the ordering is the equivalence relation defined by the objects' equals(Object) method(s):
{(x, y) such that x.equals(y)}

You are saying that null is equal to an instance with zero duration, which it is not, because zeroDuration.equals(null) is false (or, at least, it should be), and null.equals(zeroDuration) results in an exception.

You should decide either to put all null elements first, or all null elements last.

could you plz give me a lil example on how you would do it i tho i undestood it but i havent yet solved the problem — Blenner Vinicius, Feb 15 '18 at 18:36

SortBy crash violates contract

1 Answers1