The financial industry does seem to be loath to share the fruits of their efforts. There doesn’t seem to be a lot around. And certainly not much that is regularly updated. Maybe everyone is worried about sharing trade secrets, but the rules for calculations are well established and I’m guessing that everyone must be writing their own implementations or buying in over-priced modules.

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As a developer of financial systems, I’m constantly disappointed by how difficult it is to perform precise decimal arithmetic in Java. It’s fairly common knowledge that the use of double is not much use for financial calculations. As a quick example, take a look at the following piece of code.

public static void main(String arg[]) {
    BigDecimal bd = new BigDecimal("58.99").add(new BigDecimal("0.99"));
    System.out.println("BigDecimal result: " + bd);

    double d = 58.99 + 0.99;
    System.out.println("Double result: " + d);
}

You would have thought both results should be the same. However, you end up with:

BigDecimal result: 59.98
Double result: 59.980000000000004

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