抽象类从另一个类继承方法和属性

Question

I'm trying to make a class called RoomBase and it has an abstract method and two attributes, I need to make my program work so the RoomBase class inherits everything that the getRoomDetailsFromUser() does in the Room class.

RoomBase class:

public abstract class RoomBase {

    public abstract void getRoomDetailsFromUser();
    private int roomNumber;
    private int NumberOfSeats;
}

Room class:

public abstract class Room implements Bookable {
    Scanner input = new Scanner(System.in);
    private static int roomNumber;
    private static int numberOfSeats;
    private static String reservedBy = "";
    private static boolean reserved;
    private static boolean hasSmartBoard;

    /**
     * Get the attribute values from the user.
     */

    public Room(int roomNumber) {
        this.roomNumber = roomNumber;

    }

    public void getRoomDetailsFromUser() {

        System.out.print("Enter number of seats: ");
        numberOfSeats = input.nextInt();
        input.nextLine();
        System.out.print("Does this classroom have a smart board? (Y/N)");
        hasSmartBoard = input.nextLine().equalsIgnoreCase("y");

    }

    public boolean isHasSmartBoard() {
        return hasSmartBoard;
    }

    public void setHasSmartBoard(boolean hasSmartBoard) {
        this.hasSmartBoard = hasSmartBoard;
    }

    public static int getNumberOfSeats() {
        return numberOfSeats;
    }

    public void setNumberOfSeats(int numberOfSeats) {
        this.numberOfSeats = numberOfSeats;
    }

    public String getReservedBy() {
        return reservedBy;
    }

    public void setReservedBy(String reservedBy) {
        this.reservedBy = reservedBy;
    }

    public boolean isReserved() {
        return reserved;
    }

    public void setReserved(boolean reserved) {
        this.reserved = reserved;
    }


    public int getRoomNumber() {
        return roomNumber;
    }

    /**
     * Update the room to reserved and get the reserved by.
     */

    public void reserveThisRoom(){
        this.reserved = true;
        System.out.println("Enter the name of the person reserving this room: ");
        reservedBy = input.nextLine();
    }

     /**
     * Update the room to not reserved and clear the reserved by.
     */

    public void releaseThisRoom(){
        this.reserved = false;
        reservedBy = "";
        System.out.println("Room has been released\n");
    }

    public String toString() {
        String output = "\n\n******************************"
            + "\nRoom Number: " + roomNumber
            + "\nNumber of Seats: " + numberOfSeats
            + "\nReserved By: " + reservedBy
            + "\nReserved: " + reserved
            + "\nSmart Board: "+ hasSmartBoard;
        return output;
    }
}

Answer 1

I think you have to think a little bit more on the design than the implementation, let's see for example what the class hierarchy will be, and most important, why.

Does it makes any sense that the RoomBase extends or gets logic from the Room class, should not be the other way around ? so is it really Room Base a base class? Now if getRoomDetailsFromUser method's logic should be a common or base code it would not be instead on the base class but in the specific class (Room in this case), and to finish, do you really need an abstract class here at all? or does a regular base class fulfill you needs ?

Check the design and let me know if I can help you any further.

Answer 2

The question is a bit unclear, do you want to instantiate RoomBase? Or should it stay abstract. Should Room inherit from RoomBase? Seems so as the names hint this and Roob is not abstract.

To answer your question as best as I can guess: The only way I see is to make RoomBase extend Room. With this you would inherit everything in Room, not only the method. But only inheriting the method will no work, as this getRoomDetailsFromUser() uses variable only defined in Room, but not in RoomBase.

Answer 3

If I ignore the names you have given your classes, then the answer is simple:

I need to make my program work so the RoomBase class inherits everything that the getRoomDetailsFromUser() does in the Room class.

 public abstract class RoomBase extends Room {
 }

Of course you can't instantiate an abstract class, so to make use of this class you'd need to create a concrete subclass of RoomBase :

 public class BathRoom extends RoomBase {
 }

 RoomBase someBathRoom = new BathRoom();

Although this answers your question exactly, it's an unusual class hierarchy given the names. One possible more common pattern, would be:

 public interface Room extends Bookable {
      method signatures that Rooms have
 }

 public abstract class RoomBase implements Room { 
      methods common to all rooms go here 
 }

 public class BathRoom extends RoomBase {
      methods implementing abstract methods from RoomBase
      methods unique to BathRoom
 }

Note also that many Java programmers today use inheritance in moderation -- preferring composition .