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问题描述

我有一个包含超类的对象和一些子类对象的ArrayList。让我们把他们subclass1和subclass2。

有没有一种方法我可以去ArrayList和辨别哪些对象是父类,subclass1和subclass2。这样我就可以把它们放进ArrayList和ArrayList的。

这是一个过于简化的版本,但它证明什么,我希望做的事。

 公共类食品{
    私人字符串名称;
    公共食品(字符串名称){
        this.name =名称;
    }
}公共类布丁扩展食品{
    公共布丁(字符串名称){
        超(名);
    }
}公共类早餐食品扩展{
    公共早餐(字符串名称){
        超(名);
    }
}公共静态无效的主要(字符串ARGS []){
    ArrayList的<食品GT;食品=新的ArrayList();    foods.add(新的食品(香肠));
    foods.add(新的食品(培根));
    foods.add(新布丁(蛋糕));
    foods.add(新早餐(面包));
    foods.add(新布丁(海绵));
    foods.add(新的食品(米));
    foods.add(新早餐(鸡蛋));    ArrayList的<&布丁GT; PUD的=新的ArrayList();
    ArrayList的<早餐和GT; wakeupjuices =新的ArrayList();    对于(食品F:食品){
        //如果(f是布丁){puds.add(F);}
        //否则,如果(f是早餐){wakeupjuices.add(F);}
    }}


解决方案

您可以检查所需要的类型,如这样,使用的instanceof 关键字:

 的(食品F:食品)
{
    如果(F的instanceof布丁)
        puds.add(F);
    否则,如果(F的instanceof早餐)
        wakeupjuices.add(F);
}

I have an ArrayList which contains objects of the super class and some subclass objects. Let's call them subclass1 and subclass2.

Is there a way I can go ArrayList and discern which objects are SuperClass, subclass1 and subclass2. So I can put them into ArrayList and ArrayList.

This is an overly simplified version but it demonstrates what I'm hoping to do.

    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);}
    }

}
解决方案

You can check for the desired types like this, using the instanceof keyword:

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

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10-26 22:49