从抽象类层次结构中获取正确的字段？

Question

I have an Abstract class A

public abstract class A{
    private int x;
    public void doSomethingToX{...};
    public int getX(){
     return x;
    }

I have 7 classes that extend A, each of the 7 implement doSomethingToX in the same way, so I defined it in class A. If class B extends A, and I call B.doSomethingToX(), and then I call B.getX(), will I get B's X value or will I get A's?

In my real program I have an ArrayList of A objects

ArrayList<A> list;

and I call:

  list.add(new B());
   list.get(index).doSomethingToX();
   list.get(index).getX();

Will I get A's x or B's?

Answer 1

if you don't override getX() on extended classes you will get x from A.

if you override getX() you will get the value returned on overrides method.

example:

A a = new B(); a.getX();
B b = new B(); b.getX();

All the above lines will return the value of getX() overridden on Class B.

If this method was not overriden on Class B then you will get the value defined on Class A.