Constructors and polymorphism don't produce what you might expect : Polymorphism « Class Definition « Java Tutorial

1. Java Tutorial
2. Class Definition
3. Polymorphism

abstract class Glyph {
  abstract void draw();

  Glyph() {
    System.out.println("Glyph() before draw()");
    draw();
    System.out.println("Glyph() after draw()");
  }
}

class RoundGlyph extends Glyph {
  private int radius = 1;

  RoundGlyph(int r) {
    radius = r;
    System.out.println("RoundGlyph.RoundGlyph(), radius = " + radius);
  }

  void draw() {
    System.out.println("RoundGlyph.draw(), radius = " + radius);
  }
}

public class MainClass {
  public static void main(String[] args) {
    new RoundGlyph(5);
  }
}

Glyph() before draw()
RoundGlyph.draw(), radius = 0
Glyph() after draw()
RoundGlyph.RoundGlyph(), radius = 5