Collections.sort()报Comparison method violates its general contract异常解决方法

在重写Comparator类的compare的方法时，报如下的错误，还没有查到具体原因，因为相同的程序数据量不同，所以不知道是不是数据量太大导致报这个错？？？

public class ComparatorFloor implements Comparator<DormFloor> {

    public int compare(DormFloor o1, DormFloor o2) {
        if(o1.getSort()!=null && o2.getSort()!=null){
            return o1.getSort().compareTo(o2.getSort());
        }else{
            return o1.getFloorName().compareTo(o2.getFloorName());
        }
    }
    
}

java.lang.IllegalArgumentException: Comparison method violates its general contract!
    at java.util.TimSort.mergeHi(TimSort.java:899)
    at java.util.TimSort.mergeAt(TimSort.java:516)
    at java.util.TimSort.mergeCollapse(TimSort.java:441)
    at java.util.TimSort.sort(TimSort.java:245)
    at java.util.Arrays.sort(Arrays.java:1512)
    at java.util.ArrayList.sort(ArrayList.java:1454)
    at java.util.Collections.sort(Collections.java:175)
    at com.chinabnd.dorm.action.ActionFloor.detailread(ActionFloor.java:476)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:871)
    at ognl.OgnlRuntime.callAppropriateMethod(OgnlRuntime.java:1294)
    at ognl.ObjectMethodAccessor.callMethod(ObjectMethodAccessor.java:68)