Thread: Possible misuse of timer?

I am a bit inexperienced when it comes to using timers, especially in graphical programs.
I am trying to code a simple Tunnel game where the player is moving through a randomly generated tunnel and has to move left and right to avoid touching the walls.
Here is my code:

import java.awt.*;
import java.awt.event.*;
 
import javax.swing.*;
 
public class Tunnel extends JFrame{
 
	public static final  boolean empty = true;
	public static final boolean full = false;
 
	public static boolean [][] board = new boolean[400][400];
 
	public Tunnel(){ 
 
 
		add(new DrawTunnel());
 
		setTitle("Tunnel");
		setLocation(300,100);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		getContentPane().setSize(410,425);
		setSize(417,440);
 
 
 
 
 
		}
 
	public static void main (String[] args){
		Tunnel frame = new Tunnel();
		frame.setVisible(true);
	}
 
	static class DrawTunnel extends JPanel{
 
		Timer timer;
		int middle = 200;
		int width = 100;
 
		public DrawTunnel(){
 
			//create timer
			timer = new Timer (5, new TimerListener());
			timer.start();
 
			emptyBoard();
 
		}
 
		public void paintComponent(Graphics g){
 
			super.paintComponent(g);
 
			g.setColor(Color.black);
			for (int row= 0; row<board.length; row++){
				for (int col=0; col<board[row].length; col++){
					if (!board[row][col])
						drawSquare(g, row,col);
				}
			}
		}
 
		public void drawSquare(Graphics g, int x, int y){
			g.drawRect(x, y, 1, 1);
		}
 
		public void emptyBoard(){
			for (int r=0; r<board.length; r++){
				for (int c=0; c<board[r].length; c++){
					board[r][c] = true;
				}
			}
		}
 
		class TimerListener implements ActionListener{
 
			public void actionPerformed(ActionEvent e){
 
 
				for (int r = board.length-2;r>=0;r--){
					setRow(r,r+1);
				}
 
				drawTopLine(middle, width, 0);
 
				repaint();
				validate();
 
 
 
			}
 
			public void setRow(int rowOverwritten, int rowBeingCopied){
				for (int c=0; c<board[rowBeingCopied].length; c++){
					board[rowOverwritten][c] = board[rowBeingCopied][c];
				}
			}
 
			public void setRow(boolean[][] board, int rowNum, boolean [] row){
				for (int c=0; c<board[rowNum].length; c++){
					board[rowNum][c] = row[rowNum];
				}
			}
 
			public void drawTopLine(int gapMiddle, int gapWidth, int row){
 
				for (int c=0; c<board[row].length; c++){
					board[c][row] = false;
				}
				//forming gap
				for (int c = gapMiddle - (gapWidth/2); c<gapMiddle + (gapWidth/2); c++){
					board[c][row] = true;
				}
			}
		}
	}
}

When I run the program, only 1 row of pixelated "tunnel" appears at the top of the screen. Since I am not quite familiar with the Timer class and uses it for repetition, I guessed that I was misusing the timer. Where do I put the code to move all "tunnel walls" down and generate a new random one at the top?

Why don't beginners comment their code? What are all of these classes and methods supposed to do? Are we supposed to read your mind?