Is Java's BigDecimal the closest data type corresponding to C#'s Decimal?

B. Clay Shannon-B. Crow Raven picture B. Clay Shannon-B. Crow Raven · Apr 11, 2014 · Viewed 11.3k times · Source

According to the chart here, the equivalent data type in Java to C#'s Decimal is BigDecimal.

Is this really so? What's up with the "Big" preamble? There doesn't seem to be a "SmallDecimal" or "LittleDecimal" (let alone "MediumSizedDecimal") in Java.

I must say, though, that chart was the clearest thing I found on the subject; the other links here and here and here were about as clear to me as the Mississippi River after a torrential tempest.

Answer

Eric Lippert picture Eric Lippert · Apr 11, 2014

Is this really so?

They are similar but not identical. To be more specific: the Java version can represent every value that the C# version can, but the opposite is not true.

What's up with the "Big" preamble?

A Java BigDecimal can have arbitrarily much precision and therefore can be arbitrarily large. If you want to make a BigDecimal with a thousand places of precision, you go right ahead.

By contrast, a C# decimal has a fixed size; it takes up 128 bits and gives you 28 decimal places of precision.

To be more precise: both types give you numbers of the form

+/- someInteger / 10 ^ someExponent

In C#, someInteger is a 96 bit unsigned integer and someExponent is an integer between 0 and 28.

In Java, someInteger is of arbitrary size and someExponent is a signed 32 bit integer.