For a description of the rationale behind these classes, see https://jpaulm.github.io/busdtyps.html , and for an even more high-level introduction, which also talks about the problems with scientific data: https://jpaulm.github.io/datatyps.html .
This collection of data types was developed for a Brokerage application, for which the code is unfortunately no longer available. Among other things, the application supported some 200 currencies, obtaining conversion rates in real time from a currency conversion web site.
This code should be regarded more as a framework, and the user will almost certainly have to add methods as s/he develops his/her project. Look at https://github.com/jpaulm/jbdtypes/tree/master/src/main/java/com/jpaulmorrison/sample to get a flavour for how these methods are to be used.
This artifact has been added to Maven mainly to allow data types in https://github.com/jpaulm/fbp-etl (which see) to be resolved.
Note that Monetary is different from MPrice, as in the real world - they both have currency and amount, but they have slightly different attributes and methods. Also, PCPrice (PerCent Price) is different from MPrice (Monetary Price).