Bidirectionnal association in java

Well I was in a class of uml & patterns this week, and we've been asked to transform a "one-to-one" association relationship from an uml diagram (class) to java code.

Class diagram The problem is that every company must have a director, and every director must have a company. So we've been told that we can change the company cardinality from 1 to 0..1

Can someone help to find out the solution ? it may be a design pattern but i've been looking so far and i didn't find anything interesting !

Thanks