factory method

abstract class Shape {
  //  shape
  public abstract void draw();
  //   shape
  public abstract void erase();
  public String name;
  public Shape(String aName){
    name = aName;
  }
}

//  
class Circle extends Shape {
  public void draw() {
    System.out.println("It will draw a circle.");
  }
  public void erase() {
    System.out.println("It will erase a circle."); 
  }
  //  
  public Circle(String aName){
    super(aName);
  }
}
//  
class Square extends Shape {
  public void draw() { 
    System.out.println("It will draw a square."); 
  }
  public void erase() { 
    System.out.println("It will erase a square."); 
  }
  //  
  public Square(String aName){
    super(aName);
  }
}

abstract class ShapeFactory {  
  protected abstract Shape factoryMethod(String aName);
  //  anOperation Shape 
public void anOperation(String aName){
    Shape s = factoryMethod(aName);
    System.out.println("The current shape is: " + s.name);
    s.draw();
    s.erase();
  }
}

//   circle   CircleFactory
class CircleFactory extends ShapeFactory {
  //  factoryMethod , Circle 
  protected Shape factoryMethod(String aName) {
    return new Circle(aName + " (created by CircleFactory)");
  }
}
  
//   Square   SquareFactory
class SquareFactory extends ShapeFactory {
  //  factoryMethod , Square 
protected Shape factoryMethod(String aName) {
    return new Square(aName + " (created by SquareFactory)");
  }
}

class Main {
  public static void main(String[] args){
    ShapeFactory sf1 = new SquareFactory(); 
    ShapeFactory sf2 = new CircleFactory();
    sf1.anOperation("Shape one");
    sf2.anOperation("Shape two");
  }
}  

class NoThisShape extends Exception {
  public NoThisShape(String aName) {
    super(aName);
  }
}

abstract class ShapeFactory {  
  private static Shape s;
  private ShapeFactory() {}
    
  static Shape factoryMethod(String aName, String aType) throws NoThisShape{
    if (aType.compareTo("square")==0)
      return new Square(aName);
    else if (aType.compareTo("circle")==0)
      return new Circle(aName);
    else throw new NoThisShape(aType);  
  }
  
  //  anOperation Shape 
  static void anOperation(String aName, String aType) throws NoThisShape{
    s = factoryMethod(aName, aType);
    System.out.println("The current shape is: " + s.name);
    s.draw();
    s.erase();
  }
}

class Main {
  public static void main(String[] args) throws NoThisShape{
    ShapeFactory.anOperation("Shape one","circle");
    ShapeFactory.anOperation("Shape two","square");
    ShapeFactory.anOperation("Shape three", "delta");
  }
}

The current shape is: Shape one
It will draw a circle.
It will erase a circle.
The current shape is: Shape two
It will draw a square.
It will erase a square.
Exception in thread "main" NoThisShape: delta
        at ShapeFactory.factoryMethod(ShapeFactory.java:10)
        at ShapeFactory.anOperation(ShapeFactory.java:15)
        at Main.main(Main.java:5)