Call a object's or class' function with thread()?

I'm trying to use threading to make it so I can display a "loading screen" while something is loading. The main class will draw the loading icon and start a thread to have the Menu Screen start initializing all the images it needs, and when the Menu Screen is done loading everything, it sets a global Done Loading variable to true, and the main class starts drawing it.

But how do I call MenuScreen.initialize() with thread()? It gives me an error in the console that says "There is no public MenuScreen.initialize() method in the class MainClass".

Here's a trimmed version of what I have so far. The main class:

import gifAnimation.*; // used for the loading icon

Screen curScreen;
boolean doneLoading;
Sprite loadingGif;

void setup()
{
  size(600, 600);
  frameRate(30);
  loadingGif = new Sprite(this, "loading flower.gif");
  doneLoading = false;
  curScreen = new MenuScreen();
  thread("MenuScreen.initialize");
}

void draw()
{
  background(50);
  if(doneLoading) curScreen.screenDraw();
  else loadingGif.drawThis(width - 60, height - 60);
}

And the MenuScreen class, which implements a very simple Screen interface that stipulates its initialize() and screenDraw() methods:

class MenuScreen implements Screen
{
  int curSelection; // which selection item the cursor is on right now: new game, load game, etc.
  PImage backgroundImg;
  PImage cursorImg;

  MenuScreen()
  {
  }

  void initialize()
  {
    backgroundImg = loadImage("WelcomeBackground.png");
    cursorImg = loadImage("WelcomeCursor.png");
    doneLoading = true;
  }

  void screenDraw()
  {
    image(backgroundImg, 0, 0, width, height);
    text("Herro wuorld", 50, 50, 200, 200);
  }
}

I've also tried using thread("initialize") in MenuScreen's constructor, but that tries to look for an initialize function in the main class, too. I suppose I could just make the Initialize function a global function, but that doesn't seem like optimal coding standards when all I should need is a proper String for my call to thread()...