What is @Builder used for?

@Builder generates the builder pattern for a class — a fluent, chainable way to construct an object field by field, particularly useful for classes with many fields (especially optional ones) where a single large constructor call would be hard to read and easy to get wrong.

@Builder
public class Person {
    private String name;
    private int age;
    private String email;
}

Person p = Person.builder()
    .name("Ada")
    .age(34)
    .email("ada@example.com")
    .build();

Unlike a plain constructor call where argument order and meaning can be easy to mix up (especially with several parameters of the same type), the builder's named methods make each value's purpose explicit at the call site, and fields left unset simply default to their type's default value rather than requiring every field to be specified.

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