public User(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }

    public User(String firstName, String lastName, String address) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.address = address;
    }

    public User(String firstName, String lastName, int age) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.age = age;
    }

    public User(String firstName, String lastName, String address, String phoneNumber) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.address = address;
        this.phoneNumber = phoneNumber;
    }

    public User(String firstName, String lastName, String address, int age) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.address = address;
        this.age = age;
    }

    public User(String firstName, String lastName, String address, String phoneNumber, int age) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.address = address;
        this.phoneNumber = phoneNumber;
        this.age = age;
    }