问题
Is there an implementation of the following data-structure already implemented in Java:
Say I want the set for '2' ('A', 'C', 'D') but I also want the set for 'A' ('1', '2')
回答1:
You have no such data structure in the Java Collections Framework.
I suggest you the guava library you may find something useful there.
Note that what you have here is essentially a undirected graph so keep an eye out for graph libraries (for example JGraphT), or write your own.
来源：https://stackoverflow.com/questions/20002495/java-two-way-linked-set-data-structure