Draw different shape of polygon randomly

My program draw 10 polygon triangles in random sizes (width and height). The coordinate (points) of the polygon were generated using Random generator = new Random(). Since the points of the triangle and the width and height were randomly generated, how can I control the number of sizes drawn? e.g. there are 10 polygon in total, but I wanted to limit the number of different sizes e.g. only 2 or 4 different sizes.

for(int i = 0; i < 10; i++) {
   double xWidth = generator.nextDouble() * 50.0 + 20.0; // range width of triangle
   double yHeight = generator.nextDouble() * 50.0 + 20.0; // range height of triangle

   xCoord[0] = generator.nextInt(300);
   yCoord[0] = generator.nextInt(300);

   xCoord[1] = (int) (xCoord[0] - xWidth);
   xCoord[2] = (int) (xCoord[1] + (xWidth/2));         

   yCoord[1] = yCoord[0];
   yCoord[2] = (int) (yCoord[1] - yHeight);         

   triangles.add( new Polygon(xCoord,yCoord, 3));
}

From stackoverflow

• Why not just randomly generate 4 shapes and then run a different loop to pick randomly from those four shapes.

  Jessy : sounds do difficult :-(

• This code only generates the tringles, there has to be a .draw() somewhere - you just wrap that in some sort of code that picks one to four triangles - which again will need some sort of randomizer if you want those selected randomly.

• int limit = generator.nextInt(4)+1;    // [1,4]
  for(int i = 0; i < limit; i++) {
   //...
  }