+ +

@Data

Overview

+ Any class definition may be annotated with @Data to let lombok generate all the boilerplate that is associated with simple POJOs + (Plain Old Java Objects) and beans: getters for all fields, setters for all non-final fields, a useful toString, and implementations + of hashCode and equals which consider any two objects of this type with the same values for each field as equal. A + constructor is also generated containing 1 parameter for each final field, in the order the fields are defined. This constructor simply assigns + each parameter to the appropriate field. +

+ To override the access level of any getter/setter for any field, annotate the field with a @Setter or @Getter annotation + with the appropriate AccessLevel value. See the example below. For more information on how the getters/setters are generated, + see the documentation for @Getter and @Setter. +

+ All fields marked as transient will not be considered for hashCode and equals. All static fields will be + skipped entirely (not considered for any of the generated methods, and no setter/getter will be made for them). + The generated getter/setter method will be public unless you explicitly specify an AccessLevel, as shown in the example below. + Legal access levels are PUBLIC, PROTECTED, PACKAGE, and PRIVATE. +

+ If any method that would normally be generated exists in name that method will not be generated, and no warning or error is emitted. For example, + if you already have a method with signature void hashCode(int a, int b, int c), no int hashCode() method will be generated, + even though technically int hashCode() is an entirely different method. The same rule applies to the constructor, toString, + hashCode, and all getters and setters. +

+ @Data can handle generics parameters for fields just fine. In order to reduce the boilerplate when constructing objects for classes with + generics, you can use the staticConstructor parameter to generate a private constructor, as well as a static method that returns a new + instance. This way, javac will infer the variable name. Thus, by declaring like so: @Data(staticConstructor="of") class Foo<T> { private T x;} + you can create new instances of Foo by writing: Foo.of(5); instead of having to write: new Foo<Integer>(5);. +

Small print

+ Arrays are 'deep' compared/printed/hashCoded, which means that arrays that contain themselves will result in StackOverflowErrors. However, + this behaviour is no different from e.g. ArrayList. +

+ You may safely presume that the hashCode implementation used will not change between versions of lombok, however this guarantee is not set in stone; + if there's a significant performance improvement to be gained from using an alternate hash algorithm, that will be substituted in a future version. +

+ For a general idea of how lombok generated the equals, hashCode, and toString methods, check the example below. +

+ For the purposes of equality, 2 NaN (not a number) values for floats and doubles are considered equal, eventhough 'NaN == NaN' would + return false. This is analogous to java.lang.Double's equals method, and is in fact required to ensure that comparing an object + to an exact copy of itself returns true for equality. +

With Lombok

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Vanilla Java

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