java SortBy崩溃违反了合同

Question

嘿，伙计们，我有这段代码要根据持续时间进行比较，但我一直得到这个错误：

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

这是我的密码：

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);
    }
});

Answer 1

您违反了consistency with equals的要求：

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)}

你是说null等于一个持续时间为零的实例，而事实并非如此，因为zeroDuration.equals(null)是false（或者至少是it should be），并且null.equals(zeroDuration)会导致异常

你应该决定要么把所有空元素放在第一位，要么把所有空元素放在最后