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@NonNull

or: How I learned to stop worrying and love the NullPointerException.

Overview

- NEW in Lombok 0.11.10: You can use @NonNull on the parameter of a method or constructor to have lombok generate a null-check statement for you.
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- Lombok has always treated any annotation named @NonNull on a field as a signal to generate a null-check if lombok generates an entire method or constructor for you, via - for example @Data. Now, however, using lombok's own @lombok.NonNull on a parameter results in the insertion of just the null-check - statement inside your own method or constructor. -

- The null-check looks like if (param == null) throw new NullPointerException("param"); and will be inserted at the very top of your method. For constructors, the null-check - will be inserted immediately following any explicit this() or super() calls. -

- If a null-check is already present at the top, no additional null-check will be generated. -

With Lombok

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Vanilla Java

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Supported configuration keys:

lombok.nonNull.exceptionType = [NullPointerException | IllegalArgumentException] (default: NullPointerException). -: When lombok generates a null-check if statement, by default, a java.lang.NullPointerException will be thrown with the field name as the exception message. - However, you can use IllegalArgumentException in this configuration key to have lombok throw that exception, with 'fieldName is null' as exception message.
lombok.nonNull.flagUsage = [warning | error] (default: not set): Lombok will flag any usage of @NonNull as a warning or error if configured.

Small print

- Lombok's detection scheme for already existing null-checks consists of scanning for if statements that look just like lombok's own. Any 'throws' statement as - the 'then' part of the if statement, whether in braces or not, counts. The conditional of the if statement must look exactly like PARAMNAME == null. - The first statement in your method that is not such a null-check stops the process of inspecting for null-checks. -

- While @Data and other method-generating lombok annotations will trigger on any annotation named @NonNull regardless of casing or package name, - this feature only triggers on lombok's own @NonNull annotation from the lombok package. -

- A @NonNull on a primitive parameter results in a warning. No null-check will be generated. -

- A @NonNull on a parameter of an abstract method used to generate a warning; starting with version 1.16.8, this is no longer the case, to acknowledge the notion that @NonNull also has a - documentary role. For the same reason, you can annotate a method as @NonNull; this is allowed, generates no warning, and does not generate any code. -

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