Accessing subclass fields from a base class in Java

Question

I have a base class called Geometry from which a subclass of Sphere exists:

public class Geometry 
{
 String shape_name;
 String material;

 public Geometry()
 {
     System.out.println("New geometric object created.");
 }
}

and subclass:

public class Sphere extends Geometry
{
 Vector3d center;
 double radius;

 public Sphere(Vector3d coords, double radius, String sphere_name, String material)
 {
  this.center = coords;
  this.radius = radius;
  super.shape_name = sphere_name;
  super.material = material;
 }
}

I have an ArrayList that contains all the Geometry objects, and I want to iterate over it to verify that the data from the text file is read correctly. Here is my iterator method:

public static void check()
 {
  Iterator<Geometry> e = objects.iterator();
  while (e.hasNext())
  {
   Geometry g = (Geometry) e.next();
   if (g instanceof Sphere)
   {
    System.out.println(g.shape_name);
    System.out.println(g.material);
   }
  }
 }

How do I access and print the radius and fields of a Sphere center? Thanks in advance:)

Answer 1

If you want to access the properties of a subclass, you will need to apply it to the subclass.

if (g instanceof Sphere)
{
    Sphere s = (Sphere) g;
    System.out.println(s.radius);
    ....
}

-: Geometry, , . , Geometry print() - , . - :

class Geometry {
   ...
   public void print() {
      System.out.println(shape_name);
      System.out.println(material);
   }
}

class Shape extends Geometry {
   ...
   public void print() {
      System.out.println(radius);
      System.out.println(center);
      super.print();
   }
}

, , g.print() while.

Answer 2

cast ( , downcast):

((Sphere) g).radius

Answer 3

rwhat, print() ( -), downcasts toString().

public class Geometry 
{
 String shape_name;
 String material;

 public Geometry()
 {
     System.out.println("New geometric object created.");
 }

 public String toString() {
      StringBuilder result = new StringBuilder();
      result.append("Shape name: " + shape_name + "\t");
      result.append("Material: " + material + "\t");
      return result.toString();
 }
 public static void check (Geometry[] gList) {
     for (Geometry g: gList) {
         System.out.println(g.toString());
     }
 }

, check() , g . instanceof. ...

public class Sphere extends Geometry
 {
  Vector3d center;
  double radius;

  public Sphere(Vector3d coords, double radius, String sphere_name, String material)
  {
   this.center = coords;
   this.radius = radius;
   shape_name = sphere_name;
   super.material = material;
  }
  public String toString() {
      StringBuilder result = new StringBuilder();
      result.append("Radius: " + radius + "\t");
      result.append("Center: " + center.toString() + "\t");
      result.append(super.toString());
      return result.toString();
  }
 }

(, Cone) toString(), Geometry.

Answer 4

instanceof Cast . , .