this.front = front; this.back = back; this.flip = flip;
this.front = frontCaps; this.back = backCaps; this.flip = flipContents;
  public BufferCapabilities(ImageCapabilities frontCaps,			    ImageCapabilities backCaps,                            FlipContents flipContents)  {    if (front ==  null || back == null)      throw new IllegalArgumentException();    this.front = front;    this.back = back;    this.flip = flip;  }