SOLID: Liskov Substitution

example.java

class Liskov {
    public static int calculateArea(Rectangle x) {
        return x.getHeight() * x.getWidth();
    }

    public static int calculateArea(Square x) {
        return x.getHeight() * x.getHeight();
    }
}

class Rectangle {
  private int height;
  private int width;

  public Rectangle (int h, int w) {
    setHeight(h);
    setWidth(w);
  }

  public void setHeight ( int value ) {
    this.height = value;
  }

  public void setWidth ( int value ) {
    this.width = value;
  }

  public int getHeight () {
    return this.height;
  }

  public int getWidth () {
    return this.width;
  }
}

class Square extends Rectangle {

  public Square ( int h, int w ) {
    super(h, w);
  }

  public void setWidth ( int value ) {
    super.setHeight(value);
    super.setWidth(value);
  }

  public void setHeight ( int value ) {
    this.setWidth(value);
  }
}