使用任意数量的类

Question

I would appreciate any help in solving the following question.

Design and implement a subclass of GenericOrder called ComputerPartyOrder that takes an arbitrary number of different classes of ComputerPart objects, Peripheral objects, Cheese objects, Fruit objects and Service objects.

here is the code for Product class and GerericOrder class.

abstract class Product {
    protected float price;

    // return the price of a particular product
    abstract float price();

    //public getType() {
    //
    //}
}

//------------------------------------------------------------

class ComputerPart extends Product {
    public ComputerPart(float p) {
    price = p;
    }

    public float price() { return price; }
}

class Motherboard extends ComputerPart {
    protected String manufacturer;
    public Motherboard(String mfg, float p) {
    super(p);
    manufacturer = mfg;
    }
    public String getManufacturer() { return manufacturer; }
}

class RAM extends ComputerPart {
    protected int size;
    protected String manufacturer;
    public RAM(String mfg, int size, float p) {
    super(p);
    this.manufacturer = mfg;
    this.size = size;
    }
    public String getManufacturer() { return manufacturer; }
}

class Drive extends ComputerPart {
    protected String type;
    protected int speed;
    public Drive(String type, int speed, float p) {
    super(p);
    this.type = type;
    this.speed = speed;
    }
    public String getType() { return type; }
    public int getSpeed() { return speed; }
}


class Peripheral extends Product {
    public Peripheral(float p) {
    price = p;
    }
    public float price() { return price; }
}

class Printer extends Peripheral {
    protected String model;
    public Printer(String model, float p) {
    super(p);
    this.model = model;
    }
    public String getModel() { return model; }
}

class Monitor extends Peripheral {
    protected String model;
    public Monitor(String model, float p) {
    super(p);
    this.model = model;
    }
    public String getModel() { return model; }
}

class Service extends Product {
    public Service(float p) {
    price = p;
    }
    public float price() { return price; }
}

class AssemblyService extends Service {
    String provider;
    public AssemblyService(String pv, float p) {
    super(p);
    provider = pv;
    }
    public String getProvider() { return provider; }
}

class DeliveryService extends Service {
    String courier;
    public DeliveryService(String c, float p) {
    super(p);
    courier = c;
    }
    public String getCourier() { return courier; }
}

//-------------------------------------------------------
class Cheese extends Product {
    public Cheese(float p) {
    price = p;
    }
    public float price() { return price; }
}

class Cheddar extends Cheese {
    public Cheddar(float p) {
    super(p);
    }
}
class Mozzarella extends Cheese {
    public Mozzarella(float p) {
    super(p);
    }
}

class Fruit extends Product {
    public Fruit(float p) {
    price = p;
    }
    public float price() { return price; }
}
class Apple extends Fruit {
    public Apple(float p) {
    super(p);
    }
}
class Orange extends Fruit {
    public Orange(float p) {
    super(p);
    }
}

GenericOrder:

import java.util.ArrayList;
import java.util.List;

public abstract class GenericOrder<T> extends Product {
    private static long counter = 1;
    private final long id = counter++;
    private List<T> Item;

    public GenericOrder() {
        Item = new ArrayList<T>();
    }

    public long getid() {
        return id;
    }

    public void addItem(T newItem) {
        Item.add(newItem);
    }

    public List<T> getItem() {
        return Item;
    }

    public void setItem(List<T> Item) {
        this.Item = Item;
    }
}

EDIT: Code so far

public abstract class ComputerPartyOrder extends GenericOrder {
    GenericOrder GOrder = new GenericOrder() {
        @Override
        float price() {
            return 0;
        }
    };

    public void input(Product newitem) {
        GOrder.addItem(newitem);
    }

    public void output() {
        System.out.println(GOrder.getItem());
    }
}

Answer 1

You have the right idea, but GenericOrder does not need a type parameter T . Instead, you can set the type of Item to Product (the superclass of all the different types of products).

public abstract class GenericOrder extends Product {
    private static long counter = 1;
    private final long id = counter++;
    private List<Product> Item;

    public GenericOrder() {
        Item = new ArrayList<Product>();
    }

    public long getid() {
        return id;
    }

    public void addItem(Product newItem) {
        Item.add(newItem);
    }

    public List<Product> getItem() {
        return Item;
    }

    public void setItem(List<Product> Item) {
        this.Item = Item;
    }
}

You will still be able to call addItem with any instance of a subclass of Product .

I would also suggest renaming Item to item , uppercase names are usually used for types, not variables.