[jira] [Created] (KAFKA-9642) "BigDecimal(double)" should not be used

["Soontaek Lim (Jira)" <ji...@apache.org>]

Soontaek Lim created KAFKA-9642:
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             Summary: "BigDecimal(double)" should not be used
                 Key: KAFKA-9642
                 URL: https://issues.apache.org/jira/browse/KAFKA-9642
             Project: Kafka
          Issue Type: Bug
            Reporter: Soontaek Lim
            Assignee: Soontaek Lim


I recommend not to use the BigDecimal(double) constructor. Because of floating point imprecision, we're unlikely to get the value we expect from that constructor.

Instead, we should use BigDecimal.valueOf, which uses a string under the covers to eliminate floating-point rounding errors.

 

From JavaDocs

The results of this constructor can be somewhat unpredictable. One might assume that writing new BigDecimal(0.1) in Java creates a BigDecimal which is exactly equal to 0.1 (an unscaled value of 1, with a scale of 1), but it is actually equal to 0.1000000000000000055511151231257827021181583404541015625. This is because 0.1 cannot be represented exactly as a double (or, for that matter, as a binary fraction of any finite length). Thus, the value that is being passed in to the constructor is not exactly equal to 0.1, appearances notwithstanding.



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