Java - 从父类(super class)的ArrayList中排序出子类

Question

我有一个 ArrayList，其中包含父类(super class)的对象和一些子类对象。我们将它们称为 subclass1 和 subclass2。

有没有一种方法可以让我通过 ArrayList 来辨别哪些对象是 SuperClass、subclass1 和 subclass2。这样我就可以将它们放入ArrayList和ArrayList中。

这是一个过于简化的版本，但它演示了我希望做什么。

    public class food{
    private String name;
    public food(String name){
        this.name = name;
    }
}   

public class pudding extends food{
    public pudding(String name){
        super(name);
    }
}

public class breakfast extends food{
    public breakfast(String name){
        super(name);
    }
}

public static void main(String args[]){
    ArrayList<food> foods = new ArrayList();

    foods.add(new food("Sausage"));
    foods.add(new food("Bacon"));
    foods.add(new pudding("cake"));
    foods.add(new breakfast("toast"));
    foods.add(new pudding("sponge"));
    foods.add(new food("Rice"));
    foods.add(new breakfast("eggs"));

    ArrayList<pudding> puds = new ArrayList();
    ArrayList<breakfast> wakeupjuices = new ArrayList();

    for(food f : foods){
        //if(f is pudding){puds.add(f);}
        //else if(f is breakfast){wakeupjuices.add(f);}
    }

}

Answer 1

您可以使用 instanceof 关键字检查所需的类型，如下所示:

for (food f : foods)
{
    if (f instanceof pudding)
        puds.add(f);
    else if (f instanceof breakfast)
        wakeupjuices.add(f);
}