Question

我有这个compareTo函数继续，但不总是，抛出一个关于它的一般契约的错误，如果你通过Comparable类进行了排序，可能会在某个时候命中。

public int compareTo(FollowableEntity otherEntity) {
    if(followTarget == null || otherEntity == null || otherEntity.followTarget == null || !otherEntity.follows) return 0;
    if(this.followTarget != otherEntity.followTarget) return 0;
    if(this.getDistanceSqToEntity(followTarget) == otherEntity.getDistanceToEntity(followTarget) && this.getDistanceSqToEntity(otherEntity) < this.getDistanceSqToEntity(followTarget)) return 1;
    if(this.getDistanceSqToEntity(followTarget) == otherEntity.getDistanceToEntity(followTarget) && this.getDistanceSqToEntity(otherEntity) > this.getDistanceSqToEntity(followTarget)) return -1;
    if(this.getDistanceSqToEntity(followTarget) < otherEntity.getDistanceSqToEntity(followTarget) && (this.getDistanceSqToEntity(followTarget) < this.getDistanceSqToEntity(otherEntity))) return -1;
    if(this.getDistanceSqToEntity(followTarget) < otherEntity.getDistanceSqToEntity(followTarget) && (this.getDistanceSqToEntity(followTarget) > this.getDistanceSqToEntity(otherEntity))) return 1;
    if(this.getDistanceSqToEntity(followTarget) > otherEntity.getDistanceSqToEntity(followTarget)) return 1;

    return 0;

}


FollowableEntity has double position values: posX, posY, posZ.
(FollowableEntity(obj)).getDistanceSqToEntity(FollowableEntity) returns the squared distance between the entities as a double. (x1 - x)^2 + (y1 - y)^2 + (z1 - z)^2.

前两个条件在逻辑上从不会发生比较，但无论如何我把它们放在那里。

我不确定导致错误的条件是什么，因为它是唯一的一次，碰巧有数十个实体围绕彼此旋转以达到目标。

以下是日志的一部分，我的日志记录实用程序效率很低。

17:23:37 - Caused by: java.lang.IllegalArgumentException: Comparison method violates its general contract!
17:23:37 -  at java.util.ComparableTimSort.mergeLo(ComparableTimSort.java:714)
17:23:37 -  at java.util.ComparableTimSort.mergeAt(ComparableTimSort.java:451)
17:23:37 -  at java.util.ComparableTimSort.mergeCollapse(ComparableTimSort.java:376)
17:23:37 -  at java.util.ComparableTimSort.sort(ComparableTimSort.java:182)
17:23:37 -  at java.util.ComparableTimSort.sort(ComparableTimSort.java:146)
17:23:37 -  at java.util.Arrays.sort(Arrays.java:472)
17:23:37 -  at java.util.Collections.sort(Collections.java:155)

之后它指向调用Collections.sort（）的行，但没有告诉我有关compareTo函数的任何信息。

Answer 1

我前段时间遇到Comparable违反合同的行为，这与返回相互矛盾的结果有关;在某些情况下，您的方法可能会为object1.compareTo(object2)和object2.compareTo(object1)返回1（或-1）

你可以在这里找到类似的问题.-

why does my compare method throw exception -- Comparison method violates its general contract!

Java Comparable Object Sorting：compareTo（Object）错误

1 个答案: