如何为object中使用builder预初始化的属性赋值？

public class User {
    private String name;
    private int age;
    private String email;

    private User(Builder builder) {
        this.name = builder.name;
        this.age = builder.age;
        this.email = builder.email;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public String getEmail() {
        return email;
    }

    public static class Builder {
        private String name;
        private int age;
        private String email;

        public Builder(String name) {
            this.name = name;
        }

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

        public Builder setEmail(String email) {
            this.email = email;
            return this;
        }

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

// 使用示例
User user = new User.Builder("John")
                .setAge(30)
                .setEmail("john@example.com")
                .build();

System.out.println(user.getName());  // 输出 "John"
System.out.println(user.getAge());  // 输出 30
System.out.println(user.getEmail());  // 输出 "john@example.com"