An example of fullscreen sketch under multi-screen environment for Processing.

FullscreenExample.pde

// Fullscreen sketch example under multi-screen environment
// @see http://processing.org/discourse/beta/num_1185318989.html

import java.awt.*;

static final int PREFERRED_GRAPHICS_DEVICE_INDEX = 1; //< This value represents the target monitor.

Rectangle monitorBounds = new Rectangle();

public void init() {
  frame.removeNotify();
  frame.setUndecorated(true);
  frame.addNotify();
  super.init();
}

void setup() {
  GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
  GraphicsDevice[] gs = ge.getScreenDevices();
  int realScreenIndex = PREFERRED_GRAPHICS_DEVICE_INDEX;
  if (gs.length <= 1)
    realScreenIndex = 0;
  GraphicsDevice gd = gs[realScreenIndex];
  GraphicsConfiguration gc = gd.getDefaultConfiguration();
  monitorBounds = gc.getBounds();
  size(monitorBounds.width, monitorBounds.height);
  frame.setLocation(monitorBounds.x, monitorBounds.y);
}

void draw() {
  frame.setLocation(monitorBounds.x, monitorBounds.y);
  frame.setAlwaysOnTop(true);
  
  background(0);
  
  text("FPS:" + frameRate, 20, 20);
}