Change Unidirectional Association to Bidirectional
You have two classes that need to use each other’s features, but there is only a one-way link.
Add back pointers, and change modifiers to update both sets.
![](http://www.cnblogs.com/images/cnblogs_com/nanshouyong326/90398/o_20080126(020).jpg)
You have two classes that need to use each other’s features, but there is only a one-way link.
Add back pointers, and change modifiers to update both sets.