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

Literal decimal floating-point numbers cannot always be represented precisely using the double primitive type because the underlying representation of double is binary. This imprecision becomes apparent when a BigDecimal is constructed from a double.

Consequently, the BigDecimal(double val) constructor must not be invoked with floating-point literals.

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
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 precision is preserved.

// prints 0.1
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 appears to be straightforward.

Bibliography

      03. Numeric Types and Operations (NUM)      NUM11-J. Do not rely on the default string representation of floating-point values