src.com.solid.LSP.java

package src.com.solid.LSP;

class Rectangle
{
  protected int width, height;

  public Rectangle() {
  }

  public Rectangle(int width, int height) {
    this.width = width;
    this.height = height;
  }

  public int getWidth() {
    return width;
  }

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

  public int getHeight() {
    return height;
  }

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

  public int getArea() { return width*height; }

  @Override
  public String toString() {
    return "Rectangle{" +
      "width=" + width +
      ", height=" + height +
      '}';
  }

  public boolean isSquare()
  {
    return width == height;
  }
}

class Square extends Rectangle
{
  public Square() {
  }

  public Square(int size) {
    width = height = size;
  }

  @Override
  public void setWidth(int width) {
    super.setWidth(width);
    super.setHeight(width);
  }

  @Override
  public void setHeight(int height) {
    super.setHeight(height);
    super.setWidth(height);
  }
}

class RectangleFactory
{
  public static Rectangle newSquare(int side)
  {
    return new Rectangle(side, side);
  }

  public static Rectangle newRectangle(int width, int height)
  {
    return new Rectangle(width, height);
  }
}

class LSPDemo
{
  // maybe conform to ++
  static void useIt(Rectangle r)
  {
    int width = r.getWidth();
    r.setHeight(10);
    System.out.println("Expected area of " + (width*10) + ", got " + r.getArea());
  }

  public static void main(String[] args) {
    Rectangle rc = new Rectangle(2, 3);
    useIt(rc);

    Rectangle sq = new Square();
    sq.setHeight(5);
    sq.setWidth(10);
    useIt(sq);
  }
}