如何解决Java Collections.sort()比较方法违反了它的一般约定异常
如何解决Java Collections.sort()比较方法违反了它的一般约定异常
提问于 2019-06-21 21:16:42
我使用Collections.sort根据时间字段对列表进行升序排序。下面是代码
private String getShipmentInpickingTime(List<Shipments> shipments) {
logger.info("in getShipmentInpickingTime");
DateFormat sdf = new SimpleDateFormat("hh:mm");
Collections.sort(shipments, (o1, o2) -> {
try {
if ((!"null".equals(o1.getShipmentinpickingtime())
&& !StringUtils.isEmpty(o1.getShipmentinpickingtime()))
&& (!"null".equals(o2.getShipmentinpickingtime())
&& !StringUtils.isEmpty(o2.getShipmentinpickingtime()))) {
return sdf.parse(o1.getShipmentinpickingtime()).compareTo(sdf.parse(o2.getShipmentinpickingtime()));
}
} catch (ParseException e) {
e.printStackTrace();
}
int count1 = 0;
return count1;
});这个方法抛出异常--
java.lang.IllegalArgumentException: Comparison method violates its general contract.我通过谷歌了解了这个问题--它说我正在比较较大的对象和较小的对象。我试着颠倒了物体的顺序，但没有成功。
回答 1
Stack Overflow用户
发布于 2019-06-26 14:33:47
您没有提到哪行代码抛出了这个错误。我不确定您在这里使用的是哪个StringUtils，com.sun.deploy.util.StringUtils没有.isEmpty()方法。所以我重新实现了它。
以下是针对您的问题的有效代码：
public static void main(String[] args){
getShipmentInpickingTime(new ArrayList<Shipments>(){{
add(new Shipments("12:00"));
add(new Shipments("12:03"));
add(new Shipments("12:02"));
}});
}
private static void getShipmentInpickingTime(List<Shipments> shipments) {
DateFormat sdf = new SimpleDateFormat("hh:mm");
System.out.println(shipments.toString());
Collections.sort(shipments, (o1, o2) -> {
try {
if ((!"null".equals(o1.getShipmentPickingTime())
&& !(o1.getShipmentPickingTime() == null || o1.getShipmentPickingTime().length() < 1))
&& (!"null".equals(o2.getShipmentPickingTime())
&& !(o2.getShipmentPickingTime() == null || o2.getShipmentPickingTime().length() < 1))) {
return sdf.parse(o1.getShipmentPickingTime()).compareTo(sdf.parse(o2.getShipmentPickingTime()));
}
} catch (ParseException e) {
e.printStackTrace();
}
return 0;
});
System.out.println(shipments.toString());
}发货类内容：
public class Shipments {
private String shipmentPickingTime;
public Shipments(String shipmentPickingTime) {
this.shipmentPickingTime = shipmentPickingTime;
}
public String getShipmentPickingTime() {
return shipmentPickingTime;
}
public void setShipmentPickingTime(String shipmentPickingTime) {
this.shipmentPickingTime = shipmentPickingTime;
}
@Override
public String toString() {
return "Shipments{" +
"shipmentPickingTime='" + shipmentPickingTime + '\'' +
'}';
}
}输出：
[Shipments{shipmentPickingTime='12:00'}, Shipments{shipmentPickingTime='12:03'}, Shipments{shipmentPickingTime='12:02'}] [Shipments{shipmentPickingTime='12:00'}, Shipments{shipmentPickingTime='12:02'}, Shipments{shipmentPickingTime='12:03'}]
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/56704242
复制相关文章
相似问题