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

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Java Tutorial » Class Definition » Polymorphism

5. 24. 4. Constructors and polymorphism don't produce what you might expect


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

5. 24. Polymorphism
	5. 24. 1.	Polymorphism
	5. 24. 2.	An example of polymorphism
	5. 24. 3.	Downcasting and Run-Time Type Identification (RTTI)
	5. 24. 4.	Constructors and polymorphism don't produce what you might expect
	5. 24. 5.	Dynamic Method Dispatch
	5. 24. 6.	Using run-time polymorphism.

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