如何聚合抽象類？

Question

所以我試圖實現兩個類之間的聚合關係。但是，我對如何用抽象類實現它感到困惑。 有什麼建議嗎？

Beverage.java

public class Beverage { 

     private Size size; 
     private SizeFactor sizeCost; 
     private String description; 

     public Beverage(){} 

     public Size getSize(){ 
      return size; 
     } 

     public SizeFactor getSizeCost(){ 
      return sizeCost; 
     } 

     public String getDescription(){ 
      return description; 
     } 

     public void setSize(Size s){ 
      size = s; 
     } 

     public void setSizeCost(SizeFactor cost){ 
      sizeCost = cost; 
     } 

     public double cost(){ 
      return sizeCost.sizeCost(size); 
     } 

    } 

BeverageWithIngredient.java

public abstract class BeverageWithIngredient extends Beverage { 

    private Beverage drink = new Beverage(); 

    public abstract String getDescription(); 
    public abstract double cost(); 

} 

基本上，這是我想要做的事：

Answer 1

你必須注入Beverage到BeverageWithIngredient

public abstract class BeverageWithIngredient extends Beverage { 

    private Beverage drink; 

    public BeverageWithIngredient(Beverage drink) { 
     this.drink = drink; 
    } 

    public abstract String getDescription(); 
    public abstract double cost(); 
}