如何在JAVA中的泛型类中使用重写方法

Question

I don't want to damage to polymorphism by generic. But my short thought compels casting. When i didn't do that, the eclipse regarded a equals method as of Object Class. Anyone has good solution?? The Problem is in if statement of ArraySet Class. Good luck.

public class Star {

    (...)

     // Public Method
     @Override
     public boolean equals(Object anObject) { (...) }

}

public class ArraySet<E> {

    // Instance Variables
    private E[] _elements;
    (...)

    // Constructors
    @SuppressWarnings("unchecked")
    public ArraySet() {
        this._size = 0;
        this._maxSize = ArraySet.DEFAULT_MAX_SIZE;
        this._elements = (E[])new Object[this._maxSize];
    }

    (...)

    **if(((Star)this._elements[i]).equals(anElement))**

    (...)
}

public class AppController {

    // Instance Variables
    private AppView _appView;
    private ArraySet<Star> _starCollector;

    // Constructor
    public AppController() {
        this._appView = new AppView();
        this._starCollector = new ArraySet<Star>();
    }
    (...)
}

postscript: I'm studying English. So thanks for your pointing out.

Answer 1

I don't want to damage to polymorphism by generic.

You are not damaging polymorphism. Casting will break the whole point of using generics.

Here:

 if(((Star)this._elements[i]).equals(anElement))

you don't need to cast this._elements[i] to Star . Just call equals directly on this._elements[i] :

 if(this._elements[i].equals(anElement))

the eclipse regarded a equals method as of Object Class

No it does not. When you do this._elements[i].equals(anElement) , at runtime, the type of this._elements[i] will be figured out and it will call the equals method on whatever type it is, instead of Object . Basically, your Star 's equals method will be called even if you don't cast it.