As Java itself doesn't have a class for money(AFAIK), one reliable strategy would be following existing best practices & when it comes to money, Martin Fowler has provided a well one on his Book: Patterns of Enterprise Application Architecture. A brief can be found here.
But unfortunately I couldn't found any solution on Github implementing it in Java There is a good one for PHP, FYR
Also, there is a full page of explanation as well as partly implementation in Java(which you can copy/paste the raw version). If you are interested in consulting it, here it is(if still the case):
http://www.codecodex.com/wiki/Money_Utility_class
