Where is the condition I said you should put in there? That method should look more like the following at this point:
which adds the condition that the length be less than 10 in order to increase the size of the snake.
private void eat() { Actor food=getOneObjectAtOffset(0, 0, Food.class); if (food!=null){ SnakeEarth snakeEarth=(SnakeEarth)getWorld(); snakeEarth.removeObject(food); if(length<10) { snakeEarth.addArray(); snakeEarth.snake[length]=new Snake(); snakeEarth.addObject(snakeEarth.snake[length], getX(), getY()); length++; } } }