Presentation of the Java Standard API for handling Currencies, monetary values, arithmetic, and foreign exchange

1. JSR 354
Java Money and Currency API
Werner Keil
Build Manager, DevOps Expert,
Agile Coach
Maersk Line
EG Member, JSR 354
@wernerkeil

2. Werner Keil - Bio
• Consultant – Coach
• Creative Cosmopolitan
• Open Source Evangelist
• Software Architect
• Java Godfather
• JCP Executive Committee Member
• Eclipse UOMo Project Lead
• DevOps Guy
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3. Show me the Money!

4. Agenda
• History
• Motivation
• The JSR
• Virtual Currencies
• Currency Exchange
• Demos
• Q&A
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5. History
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6. Earlier Approaches
Martin Fowler:
A large proportion of the computers in this world manipulate money, so it's always
puzzled me that money isn't actually a first class data type in any mainstream
programming language.The lack of a type causes problems, the most obvious
surrounding currencies…
see http://martinfowler.com/eaaCatalog/money.html
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7. Earlier Approaches (2)
Eric Evans – Time and Money:
On project after project, software developers have to reinvent the wheel, creating
objects for simple recurring concepts such as "money" and "currency". Although
most languages have a "date" or "time" object, these are rudimentary, and do not
cover many needs, such as recurring sequences of time, durations of time, or
intervals of time. …
see http://timeandmoney.sourceforge.net/
To be quite frank, their code isn‘t more than an academic POC, factories
called dollars() or euros() are useless in real globally deployed frameworks,
but he made a good point.
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8. MoneyDance
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9. Motivation

10. Summary
• This JSR will provide a money and currency API for Java,
targeted at all users of currencies and monetary
amounts in Java.
• The API will provide support for standard ISO-4217 and Custom
(e.g. Virtual) currencies, as well as representation of a monetary amount.
• It willsupport currency arithmetic, even across different currencies, and
foreign currency exchange.
• Additionally, implementation details surrounding serialization
and thread safety are to be considered
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11. Why is it needed?
• Monetary values are a key feature to many applications.
• The existing java.util.Currency class is strictly a structure usedfor
representing ISO-4217 standard currencies.
• No standard value type to represent a monetary amount.
• No support for currency arithmetic or conversion
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12. Challenges
• Keep it simple – Remember the most common use case
•Adding currency values e.g. in an e-commerce app.
• Performance
•How to support low latency applications, such as High Frequency
Trading apps.
• Precision
•There can potentially be differing precisions specified for arithmetic,
currency exchange and formatting
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13. Challenges (2)
• Formatting
•Requirement should be to use existing Number Formats.
•However there is no existing format representing for example Indian
Rupees:
which might look something like this: 12,34,00,000
•Natural language support for non-decimal valuations for example
•
Lakhs
•
Crores
•
1 Lakh = 100,000
•
1 Crore = 100 Lakh 13

14. Challenges (3)
• Formatting
•12,34,56,000.21 is written
12 Crore, 34 Lakh, 56 Thousand Rupees and 21 Paise
• Support for non-standard rounding modes
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15. Non-standard Rounding Modes
• It is a big world, and each country has its regulations and cultural nuances
for expressing currencies in natural language, rounding policies, groupings,
etc.
• For example, in Argentina rounding is prescribed for the third digit after
the decimal point:
If the third digit is 2 or less, change it to 0 or drop it.
If the third digit is between 3 and 7, change it to 5.
If the third digit is 8 or more, add one to the second digit and drop the third digit or change it
to 0.
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16. Non-standard Rounding – Argentina
Argentina Rounding Examples
Original Number Rounded Notes
123.452 123.45 Third digit<3 round down
123.456 123.455 3<=third digit<=7 change to 5
123.459 123.46 Third digit>=8 round up
Switzerland uses a similar rounding strategy.
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17. Risks
Plan – “Money and Currency” is a formidable and dynamic category with
regional dependencies, requiring programmers, business users, international
accountants, and attorneys.
Risk – Incomplete or outdated spec
Mitigation – Resulting API should be flexible, let application developer
change implementation as needed.
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18. Risks (2)
Plan – There is also a Java dependency on JDK NumberFormat.
Risk – NumberFormat may require coordinated modifications.
Mitigation – Coordinate with JDK release;
Supply NumberFormats and similar classes that augment JDK content.
Plan – There is also a Java dependency on JDK NumberFormat.
Risk – NumberFormat may require coordinated modifications.
Mitigation – Coordinate with JDK release;
Supply NumberFormats and similar classes that augment JDK content.
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19. The JSR

20. Expert Group Members
• Credit Suisse
• Goldman Sachs
• Stephen Colebourne
• Ben Evans
• Werner Keil
• Bob Lee
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21. Supporting the JSR
• Credit Suisse
• Caxton Associates
• Goldman Sachs
• JP Morgan/Chase
• London Java Community
• Stephen Colebourne
• Werner Keil
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22. Schedule
• Targeted to Java 9
• Aiming at Java ME/Embedded 8 or 9
• Following the EC Merge and Standard/Embedded harmonization, no JSR should be SE/EE or
ME only, with very few, specialized exceptions. Money is so important, and has almost no
legacy in the JDK except java.util.Currency, that it should be supported by ALL POSSIBLE
platforms, except maybe JavaCard for now.
• With back-port to previous versions still supported and in relevant use
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23. Virtual Currencies
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24. Facebook Credits
What are Facebook Credits?
• Facebook Credits are a virtual currency you can use to buy virtual goods
in any games or apps of the Facebook platform that accept payments. You
can purchase Facebook Credits directly from within an app using your
credit card, PayPal, mobile phone and many other local payment methods.
► Hence any such purchase is practically a conversion,
similar to if you buy a foreign currency when
travelling abroad☺
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25. Top 10 Video Game Currencies
1. Gold
2. Gil
3. Rupees (not Indian;-)
4. Credits
5. Gold Rings
6. Hearts
7. Zenny
8. Potch
9. Munny
10.Nuyen 25

26. World Currencies
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27. Currency Exchange

28. Currency Conversion (JScience)
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29. Online Currency Conversion Example
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30. Trading Application Example
What happens, if we use built in java.util.Currency and Standard
JSP formats
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31. Demos

32. Q&A

33. Links
• The JSR: http://jcp.org/en/jsr/summary?
id=354
• java.net Project:
http://java.net/projects/javamoney/
• GitHub Project:
http://github.com/JavaMoney/

34. Links (2)
• Eclipse UOMo:
http://www.eclipse.org/uomo/
• JScience:
http://www.jscience.org
• JodaMoney:
http://joda-money.sourceforge.net/