+ +

@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. +

+ 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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+ 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. +

+ +

@Builder

It's like drinking tea with an extended pinky while wearing a monocle: No-hassle fancy-pants APIs for object creation!

Since

+ @Builder was introduced as experimental feature in lombok v0.11.10. +

Experimental

+ Experimental because: +

New feature - community feedback requested.
This feature will move to the core package soon.

+ Current status: sure thing - This feature will move to the core package soon. +

Overview

+ The @Builder annotation produces complex builder APIs for your classes. +

+ @Builder lets you automatically produce the code required to have your class be instantiable with code such as:
+ Person.builder().name("Adam Savage").city("San Francisco").worksAt("Mythbusters").build(); +

+ @Builder can be placed on a class, or on a constructor, or on a static method. While the "on a class" and "on a constructor" + mode are the most common use-case, @Builder is most easily explained with the "static method" use-case. +

+ A static method annotated with @Builder (from now on called the target) causes the following 7 things to be generated:

An inner static class named FooBuilder, with the same type arguments as the static method (called the builder).
In the builder: One private non-static non-final field for each parameter of the target.
In the builder: A package private no-args empty constructor.
In the builder: A 'setter'-like method for each parmeter of the target: It has the same type as that parameter and the same name. + It returns the builder itself, so that the setter calls can be chained, as in the above example.
In the builder: A build() method which calls the static method, passing in each field. It returns the same type that the + target returns.
In the builder: A sensible toString() implementation.
In the class containing the target: A builder() method, which creates a new instance of the builder.

+ Each listed generated element will be silently skipped if that element already exists (disregarding parameter counts and looking only at names). This + includes the builder itself: If that class already exists, lombok will simply start injecting fields and methods inside this already existing + class, unless of course the fields / methods to be injected already exist. +

+ Now that the "static method" mode is clear, putting a @Builder annotation on a constructor functions similarly; effectively, + constructors are just static methods that have a special syntax to invoke them: Their 'return type' is the class they construct, and their + type parameters are the same as the type parameters of the class itself. +

+ Finally, applying @Builder to a class is as if you added @AllArgsConstructor(acces = AccessLevel.PACKAGE) to the class and applied the + @Builder annotation to this all-args-constructor. Note that this constructor is only generated if there is no explicit + constructor present in the so annotated class, but this @AllArgsConstructor has priority over any other implicitly + generated lombok constructor (such as @Data and @Value). If an explicit constructor is present, no constructor is generated, + but the builder will be created with the assumption that this constructor exists. If you've written another constructor, you'll get a compilation error.
+ The solution is to either let lombok write this constructor (delete your own), or, annotate your constructor instead. +

+ The name of the builder class is FoobarBuilder, where Foobar is the simplified, title-cased form of the return type of the + target - that is, the name of your type for @Builder on constructors and types, and the name of the return type for @Builder + on static methods. For example, if @Builder is applied to a class named com.yoyodyne.FancyList<T>, then the builder name will be + FancyListBuilder<T>. If @Builder is applied to a static method that returns void, the builder will be named + VoidBuilder. +

+ The only configurable aspect of builder are the builder's class name (default: return type + 'Builder'), the build() method's name, and the + builder() method's name:
+ @Builder(builderClassName = "HelloWorldBuilder", buildMethodName = "execute", builderMethodName = "helloWorld") +

With Lombok

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Small print

+ Another strategy for fluent APIs is that the programmer using your library statically imports your 'builder' method. In this case, you might want to name your builder + method equal to your type's name. So, the builder method for a class called Person would become person(). This is nicer if the builder method + is statically imported. +

+ If the return type of your target static method is a type parameter (such as T), lombok will enforce an explicit builder class name. +

+ You don't HAVE to use @Builder to build anything; you can for example put it on a static method that has lots of parameter to improve the API of it. + In this case, we suggest you use buildMethodName = to rename the build method to execute() instead. +

+ The builder class will NOT get an auto-generated implementation of hashCode or equals methods! These would suggest that it is sensible to use + instances of a builder as keys in a set or map. However, that's not a sensible thing to do. Hence, no hashCode or equals. +

+ Generics are sorted out for you. +

+ +

@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 v0.11.10. +

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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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. +

+ +

- -

@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

@HTML_PRE@

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. -

- -

Maven or Ivy
Maven or Ivy	Lombok is in maven central. More…
Javac
NetBeans	Just put `lombok.jar` on the classpath and enable annotation processing. More…
Eclipse and STS	Run `lombok.jar` as a java app (i.e. doubleclick it, usually) to install. Also add lombok.jar to your project.
Eclipse and variants	Run `lombok.jar` as a java app (i.e. doubleclick it, usually) to install. Also add lombok.jar to your project. Supported variants: Springsource Tool Suite, JBoss Developer Studio
IDEA IntelliJ
IDEA IntelliJ	lombok doesn't (yet) work under IntelliJ. We're working on it though!
Javadoc
GWT	Lombok works with GWT. More…
Play! Framework
Play! Framework	Use Aaron Freeman's lombok play plugin.
ecj	Run `lombok.jar` as a java app (i.e. doubleclick it, usually) to install. Also add lombok.jar to your project. Supported variants: Springsource Tool Suite, JBoss Developer Studio
IDEA IntelliJ	lombok doesn't (yet) work under IntelliJ. We're working on it though!
A plugin developed by Michael Plushnikov adds support for most features.
Javadoc	First delombok your code then run javadoc on the result. More…

Overview

@NonNull

Overview

With Lombok

Vanilla Java

Small print

Small print

Lombok features

@Builder

Since

Experimental

Overview

With Lombok

Vanilla Java

Small print

@Value

Since

Overview

With Lombok

Vanilla Java

Small print

@Value

Since

Experimental

Overview

With Lombok

Vanilla Java

Small print

Putting the "Ex" in "Experimental": promoted or deleted experimental features.

Overview

Small print