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@Value

Immutable classes made very easy.

Since

- @Value was introduced as experimental feature in lombok v0.11.4. -

- @Value no longer implies @Wither since lombok v0.11.8. -

- @Value promoted to the main lombok package since lombok v0.12.0. -

Overview

- @Value is the immutable variant of @Data; all fields are made private and final by default, and setters are not generated. The class itself is also made final by default, because immutability is not something that can be forced onto a subclass. Like @Data, useful toString(), equals() and hashCode() methods are also generated, each field gets a getter method, and a constructor that covers every - argument (except final fields that are initialized in the field declaration) is also generated. -

- In practice, @Value is shorthand for: final @ToString @EqualsAndHashCode @AllArgsConstructor @FieldDefaults(makeFinal = true, level = AccessLevel.PRIVATE) @Getter, except that explicitly including an implementation of any of the relevant methods simply means that part won't be generated and no warning will be emitted. For example, if you write your own toString, no error occurs, and lombok will not generate a toString. Also, any explicit constructor, no matter the arguments list, implies lombok will not generate a constructor. If you do want lombok to generate the all-args constructor, add @AllArgsConstructor to the class. You can mark any constructor or method with @lombok.experimental.Tolerate to hide them from lombok. -

- It is possible to override the final-by-default and private-by-default behavior using either an explicit access level on a field, or by using the @NonFinal or @PackagePrivate annotations.
- It is possible to override any default behavior for any of the 'parts' that make up @Value by explicitly using that annotation. -

With Lombok

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Vanilla Java

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Supported configuration keys:

lombok.value.flagUsage = [warning | error] (default: not set): Lombok will flag any usage of @Value as a warning or error if configured.

Small print

- Look for the documentation on the 'parts' of @Value: @ToString, @EqualsAndHashCode, @AllArgsConstructor, @FieldDefaults, and @Getter. -

- For classes with generics, it's useful to have a static method which serves as a constructor, because inference of generic parameters via static methods works in java6 and avoids having to use the diamond operator. While you can force this by applying an explicit @AllArgsConstructor(staticConstructor="of") annotation, there's also the @Value(staticConstructor="of") feature, which will make the generated all-arguments constructor private, and generates a public static method named of which is a wrapper around this private constructor. -

- @Value was an experimental feature from v0.11.4 to v0.11.9 (as @lombok.experimental.Value). It has since been moved into the core package. The old annotation is still - around (and is an alias). It will eventually be removed in a future version, though. -

- It is not possible to use @FieldDefaults to 'undo' the private-by-default and final-by-default aspect of fields in the annotated class. Use @NonFinal and @PackagePrivate on the fields in the class to override this behaviour. -

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