I'm currently working on a raycaster in Java, and so far, I have the floor correctly textured. The problem, however, is that the floor doesn't scroll. In other words, when I move the camera in the projection, the floor stays the same, yet the walls move as expected. I'm really not sure what I'm doing wrong. I took almost all the code from this reference. Note that I took some liberties when pasting the code in that I used some pseudocode.

I tried applying a player offset to the tileX and tileY variables, e.g., tileX += player.x, and all I got was a floor that scrolls far too quickly and incorrectly.

for every ray:
   ... // other stuff relating to the walls above here.
   int start = (int)(wallY + wallHeight + 1);
   double directionCos = cos(rad(ray.getAngle()));
   double directionSin = sin(rad(ray.getAngle()));
   int textureDim = 16;
   for (int y = start; y < screenHeight; y++) {
       double distance = screenHeight / (2.f * y - screenHeight);
       distance /= cos(rad(player.getAngle()) - rad(ray.getAngle()));
       // The source I grabbed the code from actually appends the player's x and y to the tileX and tileY variables, but this completely messes up the textures when I try to.
       double tileX = distance * directionCos;
       double tileY = distance * directionSin;

       int textureX = Math.floorMod((int)(tileX * textureDim), textureDim);
       int textureY = Math.floorMod((int)(tileY * textureDim), textureDim);
       int rgb = floorTexture.getRGB(textureX, textureY);
       projectionFloor.setRGB((int)wallX, y, rgb);
  }

Below is an image of the floor.

Below is an animation visualizing the problem.