HogeBuilder.java

import java.util.Objects;

public class Hoge {

    public static void main(String[] args) {
        Hoge hoge = Hoge.builder().address("Nagoya").age(23).build("nanashi-san");
    }

    private String name;
    private int age;
    private String address;

    private Hoge(String name, int age, String address) {
        this.name = name;
        this.age = age;
        this.address = address;
    }

    private static class Builder {

        private int age;
        private String address;

        private Builder() {
        }

        public Hoge build(String name) {
            return new Hoge(Objects.requireNonNull(name), age, address);
        }

        public Builder address(String address) {
            this.address = Objects.requireNonNull(address);
            return this;
        }

        public Builder age(int age) {
            if (age < 20) {
                throw new IllegalArgumentException("age must be more than 20.");
            }
            this.age = age;
            return this;
        }
    }

    public static Builder builder() {
        return new Builder();
    }


}