实现比较方法的规则 [英] Rules to implement compare method

问题描述

像compareTo，必须是反身，反对称和传递，是否有任何规则来实现比较方法？
谢谢

解决方案

来自比较器API ：

1. 实现者必须确保所有x和y的sgn（compare（x，y））== -sgn（compare（y，x））。 （这意味着当且仅当compare（y，x）抛出
   异常时，compare（x，y）必须抛出异常。）


2. 实现者还必须确保该关系是传递的：（（compare（x，y）> 0）&&（compare（y，z）> 0））暗示比较（x，z）> 0.


3. 最后，实现者必须确保compare（x，y）== 0表示所有z的sgn（compare（x，z））== sgn（compare（y，z））。


4. 通常情况如此，但并非严格要求（compare（x，y）== 0）==（x.equals（y））。一般来说，违反此条件的任何
   比较器都应清楚地表明这个
   的事实。建议的语言是注意：这个比较器强加
   与equals不一致的订单。

like compareTo, that have to be "reflexive, antisymmetric and transitive", are there any rules to implement the compare method?? thanks

解决方案

From Comparator API:

1. The implementor must ensure that sgn(compare(x, y)) == -sgn(compare(y, x)) for all x and y. (This implies that compare(x, y) must throw an exception if and only if compare(y, x) throws an exception.)
2. The implementor must also ensure that the relation is transitive: ((compare(x, y)>0) && (compare(y, z)>0)) implies compare(x, z)>0.
3. Finally, the implementor must ensure that compare(x, y)==0 implies that sgn(compare(x, z))==sgn(compare(y, z)) for all z.
4. It is generally the case, but not strictly required that (compare(x, y)==0) == (x.equals(y)). Generally speaking, any comparator that violates this condition should clearly indicate this fact. The recommended language is "Note: this comparator imposes orderings that are inconsistent with equals."

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