Can you name and explain the use of the Builder pattern in Java?

The Builder pattern in Java is used for step-by-step creation of complex objects, especially when a constructor with many parameters becomes inconvenient or unreadable. It allows creating an object by calling a chain of methods, each setting a specific property, and finally calling the build() method, which returns the finished object.

Advantages:

• Improves code readability
• Allows creating immutable objects
• Avoids constructors with long parameter lists

Example:

public class User {
    private final String firstName;
    private final String lastName;
    private final int age;

    private User(Builder builder) {
        this.firstName = builder.firstName;
        this.lastName = builder.lastName;
        this.age = builder.age;
    }

    public static class Builder {
        private String firstName;
        private String lastName;
        private int age;

        public Builder setFirstName(String firstName) {
            this.firstName = firstName;
            return this;
        }

        public Builder setLastName(String lastName) {
            this.lastName = lastName;
            return this;
        }

        public Builder setAge(int age) {
            this.age = age;
            return this;
        }

        public User build() {
            return new User(this);
        }
    }
}

// Usage:
User user = new User.Builder()
    .setFirstName("Ivan")
    .setLastName("Ivanov")
    .setAge(30)
    .build();

Thus, Builder simplifies creating objects with many parameters and makes the code more maintainable.