How to represent n:n relationship in Java? - 未名空间MITBBS历史存档

国际科技财经博客移民网络热点娱乐民生时事公众号

Redian新闻

>未名空间

>Java - 爪哇娇娃

How to represent n:n relationship in Java?

How to represent n:n relationship in Java?# Java - 爪哇娇娃

g*a2005-03-16 08:03

1 楼

I have two fields: X (string) and Y(integer).
One object of X can point to zero or multiple objects of Y and vise versa.
How to represent this n to n relationship between X and Y?
Any implementing class of Map in Java can do this job?
Thanks.

g*g2005-03-16 08:03

2 楼

You better have a data structure of your own.
If n is not big or the relation is dense,
it's best to keep an n*m matrix.
Otherwise, you may have an array of objects X,
with every one instance keeping a vector pointing to Ys.
And vice versa for Y.

【在 g******a 的大作中提到】

: I have two fields: X (string) and Y(integer).
: One object of X can point to zero or multiple objects of Y and vise versa.
: How to represent this n to n relationship between X and Y?
: Any implementing class of Map in Java can do this job?
: Thanks.

g*a2005-03-16 08:03

3 楼

The later method you said is what I do right now.
I would like to think out a way for easy search and traversing.
Any more suggestions? Thx.:)

【在 g*****g 的大作中提到】

: You better have a data structure of your own.
: If n is not big or the relation is dense,
: it's best to keep an n*m matrix.
: Otherwise, you may have an array of objects X,
: with every one instance keeping a vector pointing to Ys.
: And vice versa for Y.

m*t2005-03-16 08:03

4 楼

Looks like you are looking for a bi-direction map:
http://jakarta.apache.org/commons/collections/apidocs-COLLECTIONS_3_1/org/apache/commons/collections/bidimap/package-summary.html

【在 g******a 的大作中提到】

: The later method you said is what I do right now.
: I would like to think out a way for easy search and traversing.
: Any more suggestions? Thx.:)

n*e2005-03-16 08:03

5 楼

If relationships are not intrinsic properties of X or Y, don't code them in X
or Y. Period. Imagine two scenarios. One is that you have another two
classes A and B and you want the same relationship between them. How would
you do? Code them again in A and B? The other is that what if the
relationship between X and Y change (say X is divorced with Y and get married
with Z). Modify X and Y? So don't code relationship in X or Y.
If you have a small number of Xs or Ys but dense relationships

【在 g******a 的大作中提到】

: The later method you said is what I do right now.
: I would like to think out a way for easy search and traversing.
: Any more suggestions? Thx.:)