Why don't descendants have methods?

Question

Java

I am a beginner and for some the question may seem too simple, but I still decided to ask it without solving it.

public class Figure {
    public String getName() {
        return "Figure";
    }
}


public class Line extends Figure {
    public Line(int a, int b){
        ...
    }
    public String getName() {
        return "Line";
    }
    public void move() {
        ...
    }
}


public class Rect extends Figure{
    public Rect(int a, int b){
        ...
    }
    public String getName() {
        return "Rect";
    }
    public void move() {
        ...
    }
    public void setPosition(int a, int b){
        ...
    }
}

public ArrayList<Figure> f = new ArrayList<>();
main(){
    f.add(new Line(1,2));
    f.add(new Rect(1,2));
    System.out.print(f.get(0).getName()) // почему-то печатает "Figure"
    Figure f1 = f.get(1);
    f1.move(); // этого метода в списке нет
}

The first question is why the required getName object method is not called?
The second question is why there are no methods in the list that are not in the Figure class?
but if you create an instance of the Line class and put it in a variable of the Line type, then everything works.
And what should be read in order to store instances of classes of different types in one variable (it also does not work with the Object type, the methods of these instances are not visible)?

Answer 1

It's time for me to practice teaching:
So let's look at an example. When declaring a variable, we see the following structure in front of us:
Figure f1 = new Rect(1,2);
Figure in this expression is something that can be written to the variable f1 , but other than that, it symbolizes how we perceive this variable . In other words, whatever we write there, we will perceive it as a Figure and see the methods inherent only to this class. (It is worth noting that even if we see methods only from the parent class, if we override them, the new version will be executed).
The situation is similar with lists. What class you put in <>, and the contents of this list will be perceived.
If you need to get to invisible methods, you can do 2 things:
Line f2 = (Line)f.get(0);
Or ((Line)f.get(0)).move();
But here:
f.add(new Line(1,2));
System.out.print(f.get(0).getName()) // prints "Figure" for some reason
You're making a mistake, sir. It should and will output 'Line'. And you don't have to say you're wrong. Check what you write there and how you override this method.

Answer 2

Write @Override in the descendants of the methods you are overriding. For the visibility of a method that is not in the parent, you need to cast a type of type
Line f1 = (Line) f.get(1); f1.move();