Salesforce Apex: When to use a Double versus a Decimal?

In Salesforce Apex, the choice between using a Double and a Decimal data type often depends on the context and specific requirements of your application. Here are some key differences and considerations that might lead you to choose one over the other:

1. Precision and Scale:
   • Decimal is an arbitrary precision number. This means it can handle very large numbers and perform calculations with a high degree of accuracy, which is crucial in financial applications where exactness is paramount.
   • Double, on the other hand, is a double-precision, 64-bit floating-point number. It’s less precise than Decimal and is subject to rounding errors, but it can represent a wider range of values, including very small fractions and very large numbers.
2. Performance:
   • Double has a performance advantage, particularly in complex mathematical calculations, because it’s a native primitive type and is processed faster by the CPU.
   • Decimal, being a high-precision number, consumes more resources and can be slower in performance. It’s implemented as a class in Apex, not a primitive data type.
3. Use Cases:
   • For financial calculations, currency values, or anywhere precision is critical, Decimal is the preferred choice.
   • For scientific calculations, engineering, or when dealing with very large or small numbers where exact precision is less important, Double is often used.
4. Memory Usage:
   • Double uses less memory compared to Decimal, as Decimal needs to store information about the precision and scale.
5. API and External Systems:
   • If you are integrating with external systems or APIs that expect data in a specific format, the choice between Double and Decimal might be dictated by those external requirements.
6. Salesforce Context:
   • In Salesforce, fields like currency, percent, etc., are represented as Decimal. This makes Decimal a more natural choice for operations involving these fields.
7. Compatibility and Conversion:
   • It’s also important to consider the compatibility with other data types and whether you’ll need to convert between Double and Decimal in your application. Such conversions can introduce additional complexity and potential for errors.

In summary, use Decimal when accuracy is critical, such as in financial applications, and Double when dealing with a broader range of values where slight imprecision is acceptable, such as in scientific calculations. The decision should be based on the specific needs of your application, considering factors like precision, performance, memory usage, and context within the Salesforce environment.