


Understand the Difference Between @RequiredArgsConstructor, @AllArgsConstructor, and @NoArgsConstructor in Lombok
Jan 24, 2025 am 12:09 AMLombok simplifies Java constructor creation by generating them at compile time. This guide explains three key Lombok annotations: @NoArgsConstructor
, @AllArgsConstructor
, and @RequiredArgsConstructor
.
1. Lombok Constructor Annotations
1.1 @NoArgsConstructor
: This annotation generates a constructor with no arguments. Useful for creating class instances without providing any initial values. For example:
import lombok.NoArgsConstructor; @NoArgsConstructor public class Example {}
Lombok creates a constructor equivalent to public Example() {}
.
1.2 @AllArgsConstructor
: This generates a constructor that takes one argument for each class field. Ideal for initializing all fields at object creation. Example:
import lombok.AllArgsConstructor; @AllArgsConstructor public class Person { private String name; private int age; }
Lombok creates public Person(String name, int age) { ... }
.
1.3 @RequiredArgsConstructor
: This generates a constructor for all final
fields and fields annotated with @NonNull
. Ensures essential fields are always initialized. Example:
import lombok.RequiredArgsConstructor; @RequiredArgsConstructor public class Person { private final String name; private int age; }
Lombok generates public Person(String name) { ... }
because name
is final
.
2. Choosing the Right Annotation
The best annotation depends on your specific needs:
2.1 @NoArgsConstructor
Use Cases: Use when you need a constructor with no arguments, often required by frameworks like Hibernate for entity classes. For instance:
@NoArgsConstructor @Entity public class User { @Id private Long id; private String username; }
2.2 @AllArgsConstructor
Use Cases: Use when all fields need initialization during object creation. Example:
@AllArgsConstructor public class Order { private String orderId; private String product; private int quantity; }
This allows Order order = new Order("123", "Laptop", 2);
2.3 @RequiredArgsConstructor
Use Cases: Use to guarantee initialization of essential (often final
or @NonNull
) fields. Useful for dependency injection in service classes:
@RequiredArgsConstructor public class CustomerService { private final CustomerRepository repository; private final NotificationService notificationService; }
This ensures repository
and notificationService
are initialized when creating CustomerService
.
3. Conclusion
Mastering these Lombok annotations leads to cleaner, more maintainable Java code. The choice depends on your project's requirements for object initialization and framework compatibility. For more details, see: Understand the Difference Between @RequiredArgsConstructor, @AllArgsConstructor, and @NoArgsConstructor in Lombok
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