The constructor "Sdrop(xx_xx)" does not exist.

Hi, I am working on a code (still really new) and I get the error of : The constructor "Sdrop (knitty_main)" does not exist.

void setup() {
  dh = new DisposeHandler(this);

  knittySettings = new JSONObject();``

  size(1270, 750);

  UsedFont = createFont("Arial", 16, true);


  //load Logo
  knittyLogoImage = loadImage("knitty_logo_80px.gif");

  displayButtonsGUI(); //GUI tab
  drop = new SDrop(this);
  //load BasicSettings
  knittySettingsName = "data/BasicKnittySettings.json";
  loadKnittySettingsFile();

}

Here is the code that the error links to, and the line of code that is highlighted by the error is : drop = new SDrop(this);

I am just trying to get this code to run, so that I can then use the language to alter this sketch to suit my needs. If i have asked this in the wrong place or wrong manner, I apologies.

Regards