code:

/** Explains polymorphism
  
	JAC444	Lesson 4 Slide 11
	@version 1.0, May 19, 2000
	@author Jordan Anastasiade
 */
import java.util.*;

class Shape {
  Shape(int i) {
    System.out.println("\nShape constructor called");
  }
  void cleanup() {
    System.out.println("Shape cleanup \n");
  }
}

class Circle extends Shape {
  Circle(int i) {
    super(i);
    System.out.println("\tDrawing a Circle \n");
  }
  void cleanup() {
    System.out.println("\tErasing a Circle");
    super.cleanup();		
  }
}

class Triangle extends Shape {
  Triangle(int i) {
    super(i);
    System.out.println("\tDrawing a Triangle \n");
  }
  void cleanup() {
    System.out.println("\tErasing a Triangle");
    super.cleanup();
  }
}

public class DrawSystem extends Shape {
  private Circle c;
  private Triangle t;
  private Shape[] drawObjs;
	
  DrawSystem(int nrObjs) {
    super(nrObjs);
    drawObjs = new Shape[nrObjs]; 
    c = new Circle(1);
    t = new Triangle(1);
    drawObjs[0] = c;
    drawObjs[1] = t;
    System.out.println("DrawSystem constructor finishes.\n\n");
  }
	
  void cleanup() {
    System.out.println("\n\nSystem.cleanup() begins");
    for(int i = 0; i < drawObjs.length; i++)
      drawObjs[i].cleanup();
    super.cleanup();
  }
	
  public static void main(String[] args) {
    DrawSystem x = new DrawSystem(2);

    //drawing methods
    x.cleanup();
  }
}