IllegalArgumentException or NullPointerException for Null Setter Parameters?

NullPointerException vs. IllegalArgumentException: Setting Parameters Appropriately

When designing a setter method where null is inappropriate for a property, the question arises: should you throw an IllegalArgumentException (IAE) or a NullPointerException (NPE)?

According to Java's documentation and best practices, IAE is the more appropriate choice for the following reasons:

1. Intended Usage: NPE is explicitly designed to be thrown by the runtime, while IAE is intended to indicate invalid method arguments.
2. Error Interpretation: NPE suggests a potential coding error in using null inappropriately. IAE, on the other hand, clearly conveys that the method was passed an illegal value.
3. Consistent Parameter Validation: IAE is commonly used for parameter validation, making it the default choice for all types of invalid parameters, including null.
4. Specific Error Messages: Both IAE and NPE allow custom error messages to convey specific validation details.
5. Inconsistent Use in Java API: While some parts of the Java API use NPE for null parameters, it is not a consistent practice. Following best practices and using IAE promotes consistency within your own codebase.

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