NUM10-J. Do not construct BigDecimal objects from floating-point literals

Literal decimal floating-point numbers cannot always be precisely represented as an IEEE 754 floating-point value. Consequently, the BigDecimal(double val) constructor must not be passed a floating-point literal as an argument when doing so results in an unacceptable loss of precision.

Noncompliant Code Example

This noncompliant code example passes a double value to the BigDecimal constructor. Because the decimal literal 0.1 cannot be precisely represented by a double, precision of the BigDecimal is affected.

// prints 0.1000000000000000055511151231257827021181583404541015625
// when run in FP-strict mode 
System.out.println(new BigDecimal(0.1)); 

Compliant Solution

This compliant solution passes the decimal literal as a String so that the BigDecimal(String val) constructor is invoked and the precision is preserved.

// prints 0.1
// when run in FP-strict mode 
System.out.println(new BigDecimal("0.1"));

Risk Assessment

Using the BigDecimal(double val) constructor with decimal floating-point literals can lead to loss of precision.

Automated Detection

Automated detection is straightforward.

Bibliography

[JLS 2005]
[Seacord 2015]	NUM10-J. Do not construct BigDecimal objects from floating-point literals LiveLesson