Multidimensional Array Movement

Newbie & Debugging Questions
#1

I’m making a space invaders-esk game and i have 3 rows of 11 aliens. I’ve down this by creating a multi-dimensional array of aliens As this is supposed to be an invasion the aliens need to move down the screen every so often, currently i’m using this:

 // update the game
    public void update()
    {    	
    	// schedule the aliens to move down
    	alienTimer.schedule(new TimerTask(){

			public void run() 
			{
		    	// move the aliens row by row
		    	moveAliens();
			}
    		
    	}, 1000, 2000);
		
    }

    // move the aliens row by row
    private void moveAliens()
    {
    	for(int i = (aliens.length -1); i > -1; i--)
    	{
    		for(int j = 10; j > -1; j--)
    		{
    			if(aliens[i][j] == null)
    			{
    				// Do nothing alien doesn't exist
    			}
    			else
    			{
    				// move the alien down
    				aliens[i][j].moveDown();
    			}
    		}
    	}
    }

// Alien Move Down method
// move the alien
	public void moveDown()
	{
		getPosition().y += 5;
	}

but when i run the game the after the second delay all the aliens just move down the screen without stopping for the 2 second period. I’ve also tried scheduleAtFixedRate, but it had the same result.

Anyone have any ideas, and whilst your here, how could i go about having different rows move in opposite directions left and right, eg row 1 would move left, hit the screen bounce then move right, row 2 would move right, it the screen bounce, then move left.

Thanks for any help