Comparison method violates its general contract!null

最新推荐文章于 2024-03-13 21:53:35 发布

原创最新推荐文章于 2024-03-13 21:53:35 发布 · 201 阅读

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文章讨论了在使用Java的Collections.sort方法进行排序时，Comparator的compare方法如果没有处理空值可能导致的问题。作者给出了原始代码，其中在比较对象属性时没有检查null值。为了解决这个问题，作者展示了修改后的代码，增加了对每个比较属性的空值检查，确保在比较前进行适当的处理，从而避免运行时异常。

@Override
            public int compare(）{
            }

这个错就是这个方法报出来的

原因是compare方法没有对空值进行判断，所以传进去的不能是空

所以应该先判断是否为空，在进行判断大小

例如我原来的代码是：

	Collections.sort(list, new Comparator<DealerComplaintFollow>() {
            @Override
            public int compare(DealerComplaintFollow o1, DealerComplaintFollow o2) {
                if (FOUR_HOUR_FOLLOW.equals(filed)) {
                    return o1.getFourHourFollowRate() > o2.getFourHourFollowRate() ? -1 : 1;
                } else if (CLOSED.equals(filed)) {
                    return o1.getComplaintCloseRate() > o2.getComplaintCloseRate() ? -1 : 1;
                } else if (AVERAGE_FOLLOW_DURATION.equals(filed)) {
                    return o1.getAverageFollowDuration() > o2.getAverageFollowDuration() ? 1 : -1;
                } else if (AVERAGE_CLOSED_DURATION.equals(filed)) {
                    return o1.getAverageCloseDuration() > o2.getAverageCloseDuration() ? 1 : -1;
                }
                return 0;
            }
        });

修改之后的代码就应该是：

	Collections.sort(list, new Comparator<DealerComplaintFollow>() {
            @Override
            public int compare(DealerComplaintFollow o1, DealerComplaintFollow o2) {
                if (FOUR_HOUR_FOLLOW.equals(filed)) {
                    if (Objects.isNull(o1.getFourHourFollowRate()) && Objects.isNull(o2.getFourHourFollowRate())){
                        return 0;
                    }else if (Objects.isNull(o1.getFourHourFollowRate())){
                        return 1;
                    }else if (Objects.isNull(o2.getFourHourFollowRate())){
                        return -1;
                    }
                    return o1.getFourHourFollowRate() > o2.getFourHourFollowRate() ? -1 : 1;
                } else if (CLOSED.equals(filed)) {
                    if (Objects.isNull(o1.getComplaintCloseRate()) && Objects.isNull(o2.getComplaintCloseRate())){
                        return 0;
                    }else if (Objects.isNull(o1.getComplaintCloseRate())){
                        return 1;
                    }else if (Objects.isNull(o2.getComplaintCloseRate())){
                        return -1;
                    }
                    return o1.getComplaintCloseRate() > o2.getComplaintCloseRate() ? -1 : 1;
                } else if (AVERAGE_FOLLOW_DURATION.equals(filed)) {
                    if (Objects.isNull(o1.getAverageFollowDuration()) && Objects.isNull(o2.getAverageFollowDuration())){
                        return 0;
                    }else if (Objects.isNull(o1.getAverageFollowDuration())){
                        return -1;
                    }else if (Objects.isNull(o2.getAverageFollowDuration())){
                        return 1;
                    }
                    return o1.getAverageFollowDuration() > o2.getAverageFollowDuration() ? 1 : -1;
                } else if (AVERAGE_CLOSED_DURATION.equals(filed)) {
                    if (Objects.isNull(o1.getAverageCloseDuration()) && Objects.isNull(o2.getAverageCloseDuration())){
                        return 0;
                    }else if (Objects.isNull(o1.getAverageCloseDuration())){
                        return -1;
                    }else if (Objects.isNull(o2.getAverageCloseDuration())){
                        return 1;
                    }
                    return o1.getAverageCloseDuration() > o2.getAverageCloseDuration() ? 1 : -1;
                }
                return 0;
            }
        });