JAVA：如何使用对象包装实例将ArrayList初始化为特定的类类型？

Question

Let's say we have 2 class types below:

class Cola {}
class Milk {}

And an Object instance which type is one of above classes:

public Object getDrink(boolean random){
    if(random)
        return new Cola();
    else
        return new Milk();
}
Object drink = getDrink(random);

Of course I can check the class of drink by calling drink.getClass() or drink.getClass().getCanonicalName() or so. That's ok.

My problem is that, I want to make and initialize an ArrayList of drink class type, NOT Object type.

ArrayList<Object> list   // This is NOT what I want.
ArrayList<drink.getClass()> list2   // Exactly what I want (but not right)

How can I do this?

Answer 1

Create an interface called Drink

In both Cola and Milk implement the interface Drink

Store as ArrayList <Drink> list;

Answer 2

创建一个Drink界面，修改Cola和Milk以implements Drink ，然后可以使用List<Drink> list2 。