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Money

Money is a tiny library for conveniently handling monetary amounts in Java.

Licencing

Money is released under the Apache 2.0 licence. This gives it an extremely wide scope for use in closed source, commercially licenced software and other open source projects. Please read the licence for full details.

Dependency

The project is built using Maven and it is available as a regular dependency from the Central Repository:

Group ID: com.tomgibara.money Artifact ID: money Version: 1.2.0

<dependency>
  <groupId>com.tomgibara.money</groupId>
  <artifactId>money</artifactId>
  <version>1.2.0</version>
</dependency>

Downloading

The money project is packaged as a single jar with no dependencies. The project is hosted on Github from which the following latest files may be downloaded:

Documentation

Complete javadocs are available.

Overview

The package provides four simple abstractions:

  • MoneyType – combines the notion of currency and locale to track and display monetary values.
  • Money – records a fixed monetary amount of a given type.
  • MoneyCalc – a variable monetary value used to calculate monetary amounts.
  • MoneySplitter – reliably distributes a calculated monetary amount into a number of proportioned parts.

With the exception of MoneySplitter, all of the classes implement the MoneyCalcOrigin interface to provide a standard way of accessing their monetary value in a mutable form.

The API is extremely straightforward; indications of how it can be used can be gleaned from the test cases. There are two noteworthy elements of the API. The first is that instances of MoneyType have a notion of consistency that is not directly exposed:

Calculations are always performed in the context of a MoneyType. The MoneyType may however be entirely non-specific (ie. not specifying a currency or locale). When a calculation is performed with a number of different Money values, its type may change (by becoming more specific) to ensure that the final value it generates is consistent with all the types of money in the calculation. If this is not possible an IllegalArgumentException will be thrown. For example, adding a euro denominated money amount to another that is localized to Greece will result in a final amount that is euro denominated in the Greek locale. On the other hand, attempting to US dollars to British pounds will raise an exception.

The other noteworthy aspect of the API is how it controls the precision of monetary calculations. Simply calling money.calc() will return an instance that will perform calculations at arbitrary precision, this is most often what one wants. But in some situations, where specific accounting rules are being transcribed, or where the precision of division needs to be controlled, the scale and rounding needs to be specified (see BigDecimal for an explanation of scale and rounding modes) This is done by supplying additional parameters on the creation of a MoneyCalc object like so: calc(scale, roundingMode). All numbers involved in a calculation obtained in this way are adjusted (possibly with a loss of precession) to match the specified scale prior to all arithmetic or comparison operations.

Changes

November 2014 Release 1.2.0 introduced a new method to derive calculations specifying only a scale. A new class was added to provide more control over the splitting of monetary amounts.

June 2011 Release 1.1 added support for specifying the scale of calculations (their precision) and for partitioning the values of monetary calculations in such a way that they sum to the original value.

March 2010 Release 1.0 was the initial release.