Question

I'm having difficulty trying to make my code work.

Create a subclass of Phone called SmartPhone. Make this subclass have a no-arg constructor and a constructor that takes a name, email, and phone. Override the toString method to return the required output.

Given Files:

public class Demo1 {

    public static void test(Phone p) {
        System.out.println("Getter test:");
        System.out.println(p.getName());
        System.out.println(p.getNumber());
    }

    public static void main(String[] args) {
        Phone test1 = new SmartPhone();
        Phone test2 = new SmartPhone("Alice", "8059226966", "[email protected]");
        System.out.println(test1);
        System.out.println(test2);
        System.out.println(test1);

        test(test1);
        test(test2);
    }

}

And

public class Phone
{
    protected String name;
    protected long number;

    public Phone() {
        this("None", -1);
    }

    public Phone(String name) {
        this(name, -1);
    }

    public Phone(String name, long number) {
        this.name = name;
        this.number = number;
    }

    public String getName() {
        return name;
    }

    public long getNumber() {
        return number;
    }
}

This is my code and please give me any tips or suggestions. Thanks!

public class SmartPhone extends Phone
{
    private String email;
    private String format;


    public SmartPhone()
    {

    }

    public SmartPhone(String name, String phoneNumber, String email)
    {

        super(name, Long.parseLong(phoneNumber));


        format = "Name: " + " " + "\n"
                + "Phone: " + " " + "\n"
                + "Email: " + " " + "\n"
                + "\n" + "Name: " + name + "\n"
                + "Phone: " + phoneNumber + "\n"
                + "Email: " + email + "\n";


    }

    @Override
    public String toString()
    {
        return format;
    }

}

Answer 1

You can follow this programming style.

/***********************************Phone.java*****************************/

public class Phone {

   /*
   * private data field, always keep data field to private and give access through
   * getter and setter
   */
   private String name;
   private long number;

   // no argument constructor
   public Phone() {
       this("None", -1);
   }

   /**
   *
   * @param name
   */
   public Phone(String name) {
       this(name, -1);
   }

   /**
   *
   * @param name
   * @param number
   */
   public Phone(String name, long number) {
       this.name = name;
       this.number = number;
   }

   // return name
   public String getName() {
       return name;
   }

   // return number
   public long getNumber() {
       return number;
   }

   @Override
   public String toString() {
       return "Name: " + name + "\n" + "Phone: " + number;
   }

}

/**********************************SmartPhone.java*****************************/

public class SmartPhone extends Phone {

   // private data field
   private String email;

   // no argument constructor
   public SmartPhone() {
       this.email = "None";
   }

   /**
   *
   * @param name
   * @param phoneNumber
   * @param email
   */
   public SmartPhone(String name, String phoneNumber, String email) {

       super(name, Long.parseLong(phoneNumber));
       this.email = email;

   }

   // return email
   public String getEmail() {
       return email;
   }

   // no need to declare extra global variable for set the format
   @Override
   public String toString() {

       return super.toString() + "\n" + "Email: " + email + "\n";
   }

}

/*********************************Demo1.java****************************/

public class Demo1 {

   //method test
   public static void test(Phone p) {
       System.out.println("Getter test:");
       System.out.println(p.getName());
       System.out.println(p.getNumber());
   }

   public static void main(String[] args) {
       //creating object
       Phone test1 = new SmartPhone();
       Phone test2 = new SmartPhone("Alice", "8059226966", "[email protected]");
       //display toString
       System.out.println(test1.toString());
       System.out.println(test2.toString());
       //test getters
       test(test1);
       test(test2);
   }

}

/***********************output********************************/

Name: None
Phone: -1
Email: None

Name: Alice
Phone: 8059226966
Email: [email protected]

Getter test:
None
-1
Getter test:
Alice
8059226966

Please let me know if you have any doubt or modify the answer. Thanks :)