Can't undo last move

Question

I am trying to add an undo function to this program. Here is what I have so far. I can't get the undo function to work for some reason. Any help is appreciated.
// Five.java - main program for Five-In-A-Row Program
import javax.swing.JFrame;
////////////////////////////////////////////////////// class Five
/** Five.java - Winner is able to put 5 pieces in a row.
   The Five program consists of three files:
   Five.java      - this file with main to create window.
   FiveGUI.java   - implements the GUI interface.
   FiveLogic.java - the logical functioning.
   @author Fred Swartz
   @version 2004-05-02
class Five {
    //================================================ method main
    public static void main(String[] args) {
        JFrame window = new JFrame("Five In A Row");
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setContentPane(new FiveGUI());
        window.pack();  // finalize layout
        window.setResizable(false);
        window.show();  // make window visible
    }//end main
}//endclass Five
//===========================================
// FiveGUI.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
/////////////////////////////////////////////////// class FiveGUI
/** A Graphical User Interface for a Five-In-A-Row game.
    This implements the user interface (view and controller),
    but the logic (model) is implemented in a separate class that
    knows nothing about the user interface.
    <p>This subclasses JPanel and puts the some buttons in the north,
    a graphical display of the board in the center, and
    a status field in the south.
    </p>
    <p>Exercise: This game probably originated on a Go board where
       the pieces are placed on the intersections, not in the
       empty spaces.  Change the program to put all pieces on the
       intersections.
    </p>
    <p>Exercise: The Undo button doesn't do anything.  Fix it here
       in the GUI and in the logic.
    </p>
    <p>Exercise: Create a machine player.</p>
    @author Fred Swartz
    @version 2004-05-02 Rodenbach
class FiveGUI extends JPanel {
    //=============================================== instance variables
    private GraphicsPanel boardDisplay_;
    private JTextField    statusField_ = new JTextField();
    private FiveLogic     gameLogic_ = new FiveLogic(9, 9);
    private boolean       gameOver_ = false;
    private static final Color[]  PLAYER_COLOR = {null, Color.black, Color.white};
    private static final String[] PLAYER_NAME  = {null, "BLACK", "WHITE"};
    //====================================================== constructor
    public FiveGUI() {
        //--- Create some buttons
        JButton newGameButton = new JButton("New Game");
        JButton undoButton = new JButton("Undo");
        //--- Create control panel
        JPanel controlPanel = new JPanel();
        controlPanel.setLayout(new FlowLayout());
        controlPanel.add(newGameButton);
        controlPanel.add(undoButton);
        //--- Create graphics panel
        boardDisplay_ = new GraphicsPanel();
        //--- Set the layout and add the components
        this.setLayout(new BorderLayout());
        this.add(controlPanel , BorderLayout.NORTH);
        this.add(boardDisplay_, BorderLayout.CENTER);
        this.add(statusField_ , BorderLayout.SOUTH);
        //-- Add action listeners
        newGameButton.addActionListener(new NewGameAction());
            undoButton.addActionListener(new UndoAction());
    }//end constructor
    //////////////////////////////////////////////// class GraphicsPanel
    // This is defined inside the outer class so that
    // it can use the game logic variable.
    class GraphicsPanel extends JPanel implements MouseListener {
        private static final int ROWS = 9;
        private static final int COLS = 9;
        private static final int CELL_SIZE = 30; // Pixels
        private static final int WIDTH  = COLS * CELL_SIZE;
        private static final int HEIGHT = ROWS * CELL_SIZE;
        //================================================== constructor
        public GraphicsPanel() {
            this.setPreferredSize(new Dimension(WIDTH, HEIGHT));
            this.setBackground(Color.gray);
            this.addMouseListener(this);  // Listen own mouse events.
        }//end constructor
        //============================================== paintComponent
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            //-- Paint grid (could be done once and saved).
            for (int r=1; r<ROWS; r++) {  // Horizontal lines
                g.drawLine(0, r*CELL_SIZE, WIDTH, r*CELL_SIZE);
            for (int c=1; c<COLS; c++) {
                g.drawLine(c*CELL_SIZE, 0, c*CELL_SIZE, HEIGHT);
            //-- Draw players pieces.
            for (int r=0; r<ROWS; r++) {
                for (int c=0; c<COLS; c++) {
                    int x = c * CELL_SIZE;
                    int y = r * CELL_SIZE;
                    int who = gameLogic_.getPlayerAt(r, c);
                    if (who != gameLogic_.EMPTY) {
                        g.setColor(PLAYER_COLOR[who]);
                        g.fillOval(x+2, y+2, CELL_SIZE-4, CELL_SIZE-4);
        }//end paintComponent
        //======================================== listener mousePressed
        public void mousePressed(MouseEvent e) {
            //--- map x,y coordinates into a row and col.
            int col = e.getX()/CELL_SIZE;
            int row = e.getY()/CELL_SIZE;
            int currentOccupant = gameLogic_.getPlayerAt(row, col);
            if (!gameOver_ && currentOccupant == gameLogic_.EMPTY) {
                gameLogic_.move(row, col);
                switch (gameLogic_.getGameStatus()) {
                    case 1: // Player one wins.  Game over.
                            gameOver_ = true;
                            statusField_.setText("BLACK WINS");
                            break;
                    case 2: // Player two wins.  Game over.
                            gameOver_ = true;
                            statusField_.setText("WHITE WINS");
                            break;
                    case FiveLogic.TIE:  // Tie game.  Game over.
                            gameOver_ = true;
                            statusField_.setText("TIE GAME");
                            break;
                    default: showNextPlayer();
            } else {  // Not legal
                Toolkit.getDefaultToolkit().beep();
            this.repaint();  // Show any updates to game.
        }//end mousePressed
        //========================================== ignore these events
        public void mouseClicked (MouseEvent e) {}
        public void mouseReleased(MouseEvent e) {}
        public void mouseEntered (MouseEvent e) {}
        public void mouseExited  (MouseEvent e) {}
    }//end inner class GraphicsPanel
    //======================================= untility method showNextPlayer
    private void showNextPlayer() {
       statusField_.setText(PLAYER_NAME[gameLogic_.getNextPlayer()] + " to play");
    }//end showNextPlayer
    ///////////////////////////////////////// inner class NewGameAction
    private class NewGameAction implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            gameLogic_.reset();
            gameOver_ = false;
            showNextPlayer();
            boardDisplay_.repaint();
    }//end inner class NewGameAction
     ///////////////////////////////////////// inner class NewGameAction
    private class UndoAction implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            gameLogic_.undo();
            gameOver_ = false;
            showNextPlayer();
            boardDisplay_.repaint();
    }//end inner class NewGameAction
}//end class FiveGUI
//================================================
// FiveLogic.java - Game to get 5 pieces in a row.
///////////////////////////////////////////////// class FiveLogic
/** This class implements the logic (model) for the game of
    Five-In-A-Row.
    <br/>Exercise: The undo function doesn't do anything.  Fix it.
    @author Fred Swartz
    @version 2004-05-02
class FiveLogic {
    /** Number of board rows. */
    private int maxRows_;
    /** Number of board columns. */
    private int maxCols_;
    /** The board. */
    private int[][] board_;
      /**The undo array. */
      private int[][] undoArray_;
    /** The player who moves next. */
    private int     nextPlayer_;
    /** Number of moves in the game. */
    private int     moves_ = 0;
    //-- Constants
    public  static final int EMPTY   = 0;  // The cell is empty.
    private static final int PLAYER1 = 1;
    public  static final int TIE     = -1; // Game is a tie (draw).
    //================================================== constructor
    public FiveLogic(int rows, int cols) {
        maxRows_ = rows;
        maxCols_ = cols;
        board_ = new int[maxRows_][maxCols_];
            undoArray_ = new int[maxRows_][maxCols_];
        reset();
    }//end constructor
    //================================================= getNextPlayer
    /** Returns the next player. */
    public int getNextPlayer() {
        return nextPlayer_;
    }//end getFace
    //=================================================== getPlayerAt
    /** Returns player who has played at particular row and column. */
    public int getPlayerAt(int r, int c) {
        return board_[r][c];
    }//end getPlayerAt
    //========================================================== reset
    /** Clears board to initial state. Makes first move in center. */
    public void reset() {
        for (int r=0; r<maxRows_; r++) {
            for (int c=0; c<maxCols_; c++) {
                board_[r][c] = EMPTY;
        moves_ = 0;  // No moves so far.
        nextPlayer_ = PLAYER1; 
        //-- Make first move in center.
        move(maxCols_/2, maxRows_/2);  // First player moves to center
    }//end reset
    //=========================================================== move
    /** Play a marker on the board, record it, flip players. */
    public void move(int r, int c) {
        //assert board_[r][c] == EMPTY;
            undoArray_[r][c] = board_[r][c];
        board_[r][c] = nextPlayer_;  // Record this move.
        nextPlayer_ = 3-nextPlayer_; // Flip players
        moves_++;                    // Increment number of moves.
    }//end move
    //=========================================================== undo
    /** Undo the last move made.  Don't go beyond beginning. */
    public void undo() {
                board_ = undoArray_;
               moves_--;      
    }//end undo
    //========================================== utility method count5_
    /** The count5_ utility function returns true if there are five in
        a row starting at the specified r,c position and
        continuing in the dr direcection (+1, -1) and
        similarly for the column c.
    private boolean count5_(int r, int dr, int c, int dc) {
        int player = board_[r][c];  // remember the player.
        for (int i=1; i<5; i++) {
            if (board_[r+dr*i][c+dc*i] != player) return false;
        return true;  // There were 5 in a row!
    } // count5_
    //=================================================== getGameStatus
    /** -1 = game is tie, 0 = more to play,
         1 = player1 wins, 2 = player2 wins */
    public int getGameStatus() {
        int row;
        int col;
        int n_up, n_right, n_up_right, n_up_left;
        boolean at_least_one_move;   // true if game isn't a tie
        for (row = 0; row < maxRows_; row++) {
            for (col = 0; col < maxCols_; col++) {
                int p = board_[row][col];
                if (p != EMPTY) {
                    // look at 4 kinds of rows of 5
                    //  1. a column going up
                    //  2. a row going to the right
                    //  3. a diagonal up and to the right
                    //  4. a diagonal up and to the left
                    if (row < maxRows_-4) // Look up
                        if (count5_(row, 1, col, 0)) return p;
                    if (col < maxCols_-4) { // row to right
                        if (count5_(row, 0, col, 1))  return p;
                        if (row < maxRows_-4) { // diagonal up to right
                            if (count5_(row, 1, col, 1)) return p;
                    if (col > 3 && row < maxRows_-4) { // diagonal up left
                        if (count5_(row, 1, col, -1)) return p;
                }//endif position wasn't empty
            }//endfor row
        }//endfor col
        // Neither player has won, it's tie if there are empty positions.
        // Game is finished if total moves equals number of positions.
        if (moves_ == maxRows_*maxCols_) {
            return TIE; // Game tied.  No more possible moves.
        } else {
            return 0;  // More to play.
    }//end getGameStatus
}//end class FiveLogic

Answer 1

Oh, oh, oh. I know why it clears the whole board. You are only saving the previous state of each square as a player moves to it. A player can only move to a square if it's empty. So you are only storing empty squares.
Change the move method to do this:
public void move(int r, int c) {
    //assert board_[r][c] == EMPTY;
    undoArray_ = (int[][]) board_.clone();
    board_[r][c] = nextPlayer_; // Record this move.
    nextPlayer_ = 3-nextPlayer_; // Flip players
    moves_++;  // Increment number of moves.
}