Я переписал ваш класс дома:
// House.java
public class House extends Canvas{
House(){
setSize(800,600);
}
public void paint(Graphics g){
Polygon p = new Polygon();
p.addPoint(100,50);
p.addPoint(300,50);
p.addPoint(250,100);
p.addPoint(50,100);
g.fillPolygon(p);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(new Color(0xAEAEAE));
g2.draw(new Line2D.Double(300, 50, 350, 100));
g2.draw(new Line2D.Double(350, 100, 350, 180));
g2.draw(new Line2D.Double(350, 180, 250, 180));
g.setColor(new Color(0xFFEABB));
p = new Polygon();
p.addPoint(50,100);
p.addPoint(250,100);
p.addPoint(250,180);
p.addPoint(50,180);
g.fillPolygon(p);
g.setColor(new Color(0xFFFFFF));
p = new Polygon();
p.addPoint(75,125);
p.addPoint(225,125);
p.addPoint(225,150);
p.addPoint(75,150);
g.fillPolygon(p);
}
}