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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. -

Experimental

- Experimental because: -

Various choices still have to be vetted as being the correct 'least surprise' choice: Should the class be made final by default, etc.

- Current status: positive - Currently we feel this feature may move out of experimental status with no or minor changes soon. -

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. -

- It is possible to override the final-by-default and private-by-default behaviour using either an explicit access level on a field, or by using the @NonFinal or @PackagePrivate annotations.
- It is possible to override any default behaviour 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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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. -

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