Modify the TicTacToeServer class to test for a win, loss or draw after each move. Send a message to each client that indicates the result of the game when the game is over.

// Server side of client/server Tic-Tac-Toe program. import java.awt.BorderLayout; import java.net.ServerSocket; import java.net.Socket; import java.io.IOException; import java.util.Formatter; import java.util.Scanner; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; import java.util.concurrent.locks.Condition; import javax.swing.JFrame; import javax.swing.JTextArea; import javax.swing.SwingUtilities;

public class TicTacToeServer extends JFrame { private String[] board = new String[ 9 ]; // tic-tac-toe board private JTextArea outputArea; // for outputting moves private Player[] players; // array of Players private ServerSocket server; // server socket to connect with clients private int currentPlayer; // keeps track of player with current move private final static int PLAYER_X = 0; // constant for first player private final static int PLAYER_O = 1; // constant for second player private final static String[] MARKS = { "X", "O" }; // array of marks private ExecutorService runGame; // will run players private Lock gameLock; // to lock game for synchronization private Condition otherPlayerConnected; // to wait for other player private Condition otherPlayerTurn; // to wait for other player's turn

// set up tic-tac-toe server and GUI that displays messages public TicTacToeServer() { super( "Tic-Tac-Toe Server" ); // set title of window

// create ExecutorService with a thread for each player runGame = Executors.newFixedThreadPool( 2 ); gameLock = new ReentrantLock(); // create lock for game

// condition variable for both players being connected otherPlayerConnected = gameLock.newCondition();

// condition variable for the other player's turn otherPlayerTurn = gameLock.newCondition();

for ( int i = 0; i < 9; i++ ) board[ i ] = new String( "" ); // create tic-tac-toe board players = new Player[ 2 ]; // create array of players currentPlayer = PLAYER_X; // set current player to first player try { server = new ServerSocket( 12345, 2 ); // set up ServerSocket } // end try catch ( IOException ioException ) { ioException.printStackTrace(); System.exit( 1 ); } // end catch

outputArea = new JTextArea(); // create JTextArea for output add( outputArea, BorderLayout.CENTER ); outputArea.setText( "Server awaiting connections " );

setSize( 300, 300 ); // set size of window setVisible( true ); // show window } // end TicTacToeServer constructor

// wait for two connections so game can be played public void execute() { // wait for each client to connect for ( int i = 0; i < players.length; i++ ) { try // wait for connection, create Player, start runnable { players[ i ] = new Player( server.accept(), i ); runGame.execute( players[ i ] ); // execute player runnable } // end try catch ( IOException ioException ) { ioException.printStackTrace(); System.exit( 1 ); } // end catch } // end for

gameLock.lock(); // lock game to signal player X's thread

try { players[ PLAYER_X ].setSuspended( false ); // resume player X otherPlayerConnected.signal(); // wake up player X's thread } // end try finally { gameLock.unlock(); // unlock game after signalling player X } // end finally } // end method execute // display message in outputArea private void displayMessage( final String messageToDisplay ) { // display message from event-dispatch thread of execution SwingUtilities.invokeLater( new Runnable() { public void run() // updates outputArea { outputArea.append( messageToDisplay ); // add message } // end method run } // end inner class ); // end call to SwingUtilities.invokeLater } // end method displayMessage

// determine if move is valid public boolean validateAndMove( int location, int player ) { // while not current player, must wait for turn while ( player != currentPlayer ) { gameLock.lock(); // lock game to wait for other player to go

try { otherPlayerTurn.await(); // wait for player's turn } // end try catch ( InterruptedException exception ) { exception.printStackTrace(); } // end catch finally { gameLock.unlock(); // unlock game after waiting } // end finally } // end while

// if location not occupied, make move if ( !isOccupied( location ) ) { board[ location ] = MARKS[ currentPlayer ]; // set move on board currentPlayer = ( currentPlayer + 1 ) % 2; // change player

// let new current player know that move occurred players[ currentPlayer ].otherPlayerMoved( location );

gameLock.lock(); // lock game to signal other player to go

try { otherPlayerTurn.signal(); // signal other player to continue } // end try finally { gameLock.unlock(); // unlock game after signaling } // end finally

return true; // notify player that move was valid } // end if else // move was not valid return false; // notify player that move was invalid } // end method validateAndMove

// determine whether location is occupied public boolean isOccupied( int location ) { if ( board[ location ].equals( MARKS[ PLAYER_X ] ) || board [ location ].equals( MARKS[ PLAYER_O ] ) ) return true; // location is occupied else return false; // location is not occupied } // end method isOccupied

// place code in this method to determine whether game over public boolean isGameOver() { return false; // this is left as an exercise } // end method isGameOver

// private inner class Player manages each Player as a runnable private class Player implements Runnable { private Socket connection; // connection to client private Scanner input; // input from client private Formatter output; // output to client private int playerNumber; // tracks which player this is private String mark; // mark for this player private boolean suspended = true; // whether thread is suspended

// set up Player thread public Player( Socket socket, int number ) { playerNumber = number; // store this player's number mark = MARKS[ playerNumber ]; // specify player's mark connection = socket; // store socket for client try // obtain streams from Socket { input = new Scanner( connection.getInputStream() ); output = new Formatter( connection.getOutputStream() ); } // end try catch ( IOException ioException ) { ioException.printStackTrace(); System.exit( 1 ); } // end catch } // end Player constructor

// send message that other player moved public void otherPlayerMoved( int location ) { output.format( "Opponent moved " ); output.format( "%d ", location ); // send location of move output.flush(); // flush output } // end method otherPlayerMoved

// control thread's execution public void run() { // send client its mark (X or O), process messages from client try { displayMessage( "Player " + mark + " connected " ); output.format( "%s ", mark ); // send player's mark output.flush(); // flush output

// if player X, wait for another player to arrive if ( playerNumber == PLAYER_X ) { output.format( "%s %s", "Player X connected", "Waiting for another player " ); output.flush(); // flush output

gameLock.lock(); // lock game to wait for second player

try { while( suspended ) { otherPlayerConnected.await(); // wait for player O } // end while } // end try catch ( InterruptedException exception ) { exception.printStackTrace(); } // end catch finally { gameLock.unlock(); // unlock game after second player } // end finally

// send message that other player connected output.format( "Other player connected. Your move. " ); output.flush(); // flush output } // end if else { output.format( "Player O connected, please wait " ); output.flush(); // flush output } // end else

// while game not over while ( !isGameOver() ) { int location = 0; // initialize move location

if ( input.hasNext() ) location = input.nextInt(); // get move location

// check for valid move if ( validateAndMove( location, playerNumber ) ) { displayMessage( " location: " + location ); output.format( "Valid move. " ); // notify client output.flush(); // flush output } // end if else // move was invalid { output.format( "Invalid move, try again " ); output.flush(); // flush output } // end else } // end while } // end try finally { try { connection.close(); // close connection to client } // end try catch ( IOException ioException ) { ioException.printStackTrace(); System.exit( 1 ); } // end catch } // end finally } // end method run

// set whether or not thread is suspended public void setSuspended( boolean status ) { suspended = status; // set value of suspended } // end method setSuspended } // end class Player } // end class TicTacToeServer