javaxannotationNonnull

javax.annotation.Nonnull is an annotation provided by the Javax Annotations API, which is part of the Java Community Process (JSR 250). It is used to indicate that a method parameter, return value, or field should not be null. This annotation is part of the JavaBeans specification and is used to improve code quality and reduce the likelihood of NullPointerExceptions.

The @Nonnull annotation can be applied to various elements in Java code, including:

Method parameters: Indicates that the parameter should not be null.

Return values: Indicates that the return value should not be null.

Fields: Indicates that the field should not be null.

Local variables: Indicates that the local variable should not be null.

When the @Nonnull annotation is used, it serves as a contract between the developer and the code that uses the annotated element. It is a way to document the expected behavior of the code and to enforce it at runtime, if desired.

The @Nonnull annotation is often used in conjunction with other annotations, such as @Nullable, which indicates that a value may be null. Together, these annotations can help to improve the robustness and reliability of Java code.

It is important to note that the @Nonnull annotation is not enforced by the Java compiler or runtime. It is up to the developer to ensure that the annotated elements adhere to the contract. However, there are tools and libraries available that can help to enforce the @Nonnull annotation at runtime, such as the Checker Framework.

In summary, the @Nonnull annotation is a useful tool for improving code quality and reducing the likelihood of NullPointerExceptions. It is part of the JavaBeans specification and is used to indicate that a method parameter, return value, or field should not be null. While it is not enforced by the Java compiler or runtime, it can be enforced using tools and libraries.