如何创建一些对象来存储在一个arrayList中，这是一个子类的属性，来自Java中的父类？

Question

So I have 3 classes, Lair, LairLocation & Minion. I created an ArrayList, which is supposed to store Minion objects, and this is an attribute of LairLocation. I'm supposed to create some objects to store in ArrayList, from the parent class Lair. Both LairLocation and Minion and sub-classes of Lair.

Whenever I try to create objects to store in ArrayList form my parent, I keep getting an error saying 'minion cannot be resolved' and telling me to create a local variable etc. Please help

LairLocation 

'''
public class LairLocations extends Lair
{
        public static ArrayList<Minion> minions = new ArrayList<Minion>();
}
'''

Lair

'''
public class Lair
{
        public void createMinions() 
    {
        minions.add("12", "Mine", "Me");//This is giving me the error 
    }
}
'''

Minion
'''
public class Minion extends Lair
{

    private String id;
    private String fName;
    private String lName;

    public Minion(String Id, String fName, String lName) 
    {
        this.id = id;
        this.fName = fName;
        this.lName = lName;
    }
}
'''

Answer 1

You're trying to access a field of a subclass from its parent class. This does not work this way.

You can only access fields of a parent class (if they're public or protected).

So, you either have to move your minions field to the parent class Lair (and make it non-static, by the way), or access this object via LairLocation class: LairLocation.minions() (if the field is supposed to be static).

Also, this line of code is incorrect: minions.add("12", "Mine", "Me");

The add() method accepts only one element.

It should probably be: minions.add(new Minion("12", "Mine", "Me"));

Answer 2

你必须调用new Minion()来获得一个新的奴才。

minions.add( new Minion( "12", "Mine", "Me") );