The @ToString annotation is one of the annotations in the project Lombok.
Note: Refer to What is the @ToString annotation in Lombok? for the introduction of the annotation.
The @ToString annotation generates an implementation for the toString() method where the class name, along with each field in order, separated by commas, is printed. But sometimes, there is a need to exclude only specific fields in the string representation of the fields.
For example, consider a Person class with three attributes - name, age, and address.
@ToString
@AllArgsConstructor
class Person {
private int age;
private String name;
private String address;
}
We define an instance of the Person class:
Person person = new Person(30, "sam", "US");
The default string representation of the object above is as follows:
Person(age=30, name=sam, address=US)
All the fields are present in the output. What if we don’t want specific fields in the output and we want to only exclude the name field?
Person(age=30, address=US)
@ToString.Exclude indicates which fields have to be excluded in the string representation of the object. To exclude a field annotate the respective field with @ToString.Exclude.
Let’s look at the code below:
import lombok.AllArgsConstructor;
import lombok.ToString;
public class Main {
@AllArgsConstructor
@ToString
static class Person {
private final int age;
@ToString.Exclude
private final String name;
private final String address;
}
public static void main(String[] args) {
Person person = new Person(30, "sam", "US");
System.out.println("Person object - " + person);
}
}ToString annotations.Person class annotated with @AllArgsConstructor and @ToString annotations.age field.name field annotated with @ToString.Exclude.address field.Person class.The string representation of the person instance contains all fields except name.