Lombok • @AllArgsConstruct vs @RequiredArgsConstructor
Overview
What is the difference between @AllArgsConstruct and @RequiredArgsConstructor in Lombok? The main difference between @AllArgsConstructor and @RequiredArgsConstructor is in the fields that are included in the generated constructor.
@AllArgsConstructor generates a constructor that takes in all fields in the class as arguments, while @RequiredArgsConstructor generates a constructor that takes in only the final or @NonNull fields as arguments.
Here’s an example to illustrate the difference:
import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NonNull;
import lombok.RequiredArgsConstructor;
@Getter
@AllArgsConstructor
@RequiredArgsConstructor
public class Example {
private final String foo;
private int bar;
@NonNull private String baz;
}
The De-Lombok code (generated) from above example
public class Example {
private final String foo;
private int bar;
private final String baz;
public Example(String foo, int bar, String baz) {
this.foo = foo;
this.bar = bar;
this.baz = baz;
}
public Example(String foo, String baz) {
this(foo, 0, baz);
}
public String getFoo() {
return this.foo;
}
public int getBar() {
return this.bar;
}
public void setBar(int bar) {
this.bar = bar;
}
public String getBaz() {
return this.baz;
}
}
In the above code, the Lombok annotations @Getter, @AllArgsConstructor, @NonNull, and @RequiredArgsConstructor have been replaced with the explicit constructor and getter and setter methods.
Lombok’s @NonNull annotation has been replaced by a final field declaration, which ensures that baz is not null.
Lombok’s @AllArgsConstructor has been replaced with a constructor that takes in all three fields as arguments, and Lombok’s @RequiredArgsConstructor has been replaced with a constructor that takes in only foo and baz as arguments, with a default value of 0 for bar.
The @AllArgsConstructor will generate a constructor with three arguments, one for each of foo, bar, and baz. @RequiredArgsConstructor will generate a constructor with two arguments, one for foo and one for baz.
You can then create an instance of Example using these constructors like this:
Example example1 = new Example("hello", 42, "world");
Example example2 = new Example("hello", "world");
As you can see, example1 uses the constructor generated by @AllArgsConstructor, which includes all three fields, while example2 uses the constructor generated by @RequiredArgsConstructor, which includes only foo and baz.
In general, you would use @AllArgsConstructor when you want to generate a constructor that includes all fields, and @RequiredArgsConstructor when you want to generate a constructor that includes only the required fields.
In Conclusion
In conclusion, the choice between using @AllArgsConstructor and @RequiredArgsConstructor in Lombok ultimately depends on the specific needs of your code. If you want to generate a constructor that includes all fields, then @AllArgsConstructor is the way to go. On the other hand, if you only want to include the required fields in the constructor, then @RequiredArgsConstructor is the better option. Both annotations provide a convenient way to generate constructors without having to manually write them, saving developers valuable time and effort. Lombok’s annotations can make your code more concise, readable, and maintainable, making it a valuable tool in any developer’s toolkit.
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