MultiJava

include rMoveTo;

class Polymorph {
   public static void main(String argv[]) {
      Polymorph obj = new Polymorph();
   }

   Polymorph() {
      // create some shape instances
      Shape scribble[] = new Shape[2];
      scribble[0] = new Rectangle(10, 20, 5, 6);
      scribble[1] = new Circle(15, 25, 8);

      // iterate through the list and handle shapes polymorphically
      for (int i = 0; i < scribble.length; i++) {
         draw(scribble[i]);
         scribble[i].rMoveTo(100, 100);
         draw(scribble[i]);
      }

      // call a rectangle specific function
      Rectangle arect = new Rectangle(0, 0, 15, 15);
      arect.setWidth(30);
      draw(arect);
   }
}

// draw - introduce method (internal)
void Polymorph.draw(Shape self) {}

// draw - dispatch on rectangle instance
void Polymorph.draw(Shape@Rectangle self) {
   System.out.println("Drawing a Rectangle at:(" + self.getX() + ", " + self.getY() +
      "), width " + self.getWidth() + ", height " + self.getHeight());
}

// draw - dispatch on circle instance
void Polymorph.draw(Shape@Circle self) {
   System.out.println("Drawing a Circle at:(" + self.getX() + ", " + self.getY() +
      "), radius " + self.getRadius());
}

abstract class Shape {
   private int x;
   private int y;

   // constructor
   Shape(int newx, int newy) {
      moveTo(newx, newy);
   }

   // move the x & y position
   void moveTo(int newx, int newy) {
      setX(newx);
      setY(newy);
   }

   // accessors for x & y
   int getX() { return x; }
   int getY() { return y; }
   void setX(int newx) { x = newx; }
   void setY(int newy) { y = newy; }
}

// Shape: introduce relative move method (external)
void Shape.rMoveTo(int deltax, int deltay) {
   moveTo(getX() + deltax, getY() + deltay);
}

class Rectangle extends Shape {
   private int width;
   private int height;

   // constructor
   Rectangle(int newx, int newy, int newwidth, int newheight) {
      super(newx, newy);
      setWidth(newwidth);
      setHeight(newheight);
   }

   // accessors for the width & height
   int getWidth() { return width; }
   int getHeight() { return height; }
   void setWidth(int newwidth) { width = newwidth; }
   void setHeight(int newheight) { height = newheight; }
}

class Circle extends Shape {
   private int radius;

   // constructor
   Circle(int newx, int newy, int newradius) {
      super(newx, newy);
      setRadius(newradius);
   }

   // accessors for the radius
   int getRadius() { return radius; }
   void setRadius(int newradius) { radius = newradius; }
}

Drawing a Rectangle at:(10, 20), width 5, height 6
Drawing a Rectangle at:(110, 120), width 5, height 6
Drawing a Circle at:(15, 25), radius 8
Drawing a Circle at:(115, 125), radius 8
Drawing a Rectangle at:(0, 0), width 30, height 15