You should be using IllegalArgumentException (IAE), not NullPointerException (NPE) for the following reasons: First, the NPE JavaDoc explicitly lists the cases where NPE is appropriate. Notice that all of them are thrown by the runtime when null is used inappropriately. In contrast, the IAE JavaDoc couldn’t be more clear: “Thrown to indicate that a method … Read more
The field annotated @Autowired is null because Spring doesn’t know about the copy of MileageFeeCalculator that you created with new and didn’t know to autowire it. The Spring Inversion of Control (IoC) container has three main logical components: a registry (called the ApplicationContext) of components (beans) that are available to be used by the application, … Read more
Since JSR 305 (whose goal was to standardize @NonNull and @Nullable) has been dormant for several years, I’m afraid there is no good answer. All we can do is to find a pragmatic solution and mine is as follows: Syntax From a purely stylistic standpoint I would like to avoid any reference to IDE, framework … Read more
No, a null check is not needed before using instanceof. The expression x instanceof SomeClass is false if x is null. The Java 11 Language Specification expresses this concisely in section 15.20.2, “Type comparison operator instanceof”. (Java 17 expresses this less concisely, after the introduction of instanceof patternmatching.) “At run time, the result of the … Read more