Não entendi o código Tic Tac Toe do applet java

Bom dia!!!

Eu vim procurar ajuda quanto ao entendimento daquele
código de applet do Tic Tac Toe que vem junto com o j2sdk1.4.2.
Eu tenho 3 dúvidas:
1º Qual a sequência do programa? Isto é, por onde começa e
por onde termina o jogo? Eu acho que o início é pelo método
de escuta do mouse no applet, mas só até aí.
2º O código possui uma única classe. Então, quando são chamados
os métodos?
3º Não entendi também o uso do deslocamento de bits para esquerda
em todo o código. Não entendi para que serve!
O código vai abaixo.

Quem puder me ajudar estará me prestando um grande favor
e ficarei muito grata.

Aguardo respostas! Obrigada!

Copyright © 2003 Sun Microsystems, Inc. All Rights Reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
-Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
-Redistribution in binary form must reproduct the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the distribution.
Neither the name of Sun Microsystems, Inc. or the names of contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
This software is provided “AS IS,” without a warranty of any kind. ALL
EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS SHALL NOT
BE LIABLE FOR ANY DAMAGES OR LIABILITIES SUFFERED BY LICENSEE AS A RESULT
OF OR RELATING TO USE, MODIFICATION OR DISTRIBUTION OF THE SOFTWARE OR ITS
DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE SOFTWARE, EVEN
IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
You acknowledge that Software is not designed, licensed or intended for
use in the design, construction, operation or maintenance of any nuclear
facility.
*/

@(#)TicTacToe.java 1.8 03/01/23
*/

import java.awt.<em>;

import java.awt.event.</em>;

import java.awt.image.<em>;

import <a href="http://java.net">java.net</a>.</em>;

import java.applet.*;

/**

A TicTacToe applet. A very simple, and mostly brain-dead
implementation of your favorite game! <p>
In this game a position is represented by a white and black
bitmask. A bit is set if a position is ocupied. There are
9 squares so there are 1<<9 possible positions for each
side. An array of 1<<9 booleans is created, it marks
all the winning positions.
@version 1.2, 13 Oct 1995
@author Arthur van Hoff
@modified 04/23/96 Jim Hagen : winning sounds

@modified 02/10/98 Mike McCloskey : added destroy()

<em>/

public

class TicTacToe extends Applet implements MouseListener {

/</em>*

White’s current position. The computer is white.
*/
int white;

/**

Black’s current position. The user is black.
*/
int black;

/**

The squares in order of importance…
*/
final static int moves[] = {4, 0, 2, 6, 8, 1, 3, 5, 7};

/**

The winning positions.
*/
static boolean won[] = new boolean[1 << 9];
static final int DONE = (1 << 9) - 1;
static final int OK = 0;
static final int WIN = 1;
static final int LOSE = 2;
static final int STALEMATE = 3;

/**

Mark all positions with these bits set as winning.
*/
static void isWon(int pos) {
for (int i = 0 ; i < DONE ; i++) {
if ((i & pos) == pos) {
won[i] = true;
}
}
}

/**

Initialize all winning positions.
*/
static {
isWon((1 << 0) | (1 << 1) | (1 << 2));
isWon((1 << 3) | (1 << 4) | (1 << 5));
isWon((1 << 6) | (1 << 7) | (1 << 8));
isWon((1 << 0) | (1 << 3) | (1 << 6));
isWon((1 << 1) | (1 << 4) | (1 << 7));
isWon((1 << 2) | (1 << 5) | (1 << 8));
isWon((1 << 0) | (1 << 4) | (1 << 8));
isWon((1 << 2) | (1 << 4) | (1 << 6));
}

/**

Compute the best move for white.
@return the square to take
*/
int bestMove(int white, int black) {
int bestmove = -1;

loop:

for (int i = 0 ; i < 9 ; i++) {

int mw = moves[i];

if (((white & (1 << mw)) == 0) && ((black & (1 << mw)) == 0)) {

int pw = white | (1 << mw);

if (won[pw]) {

// white wins, take it!

return mw;

}

for (int mb = 0 ; mb < 9 ; mb++) {

if (((pw & (1 << mb)) == 0) && ((black & (1 << mb)) == 0)) {

int pb = black | (1 << mb);

if (won[pb]) {

// black wins, take another

continue loop;

}

}

}

// Neither white nor black can win in one move, this will do.

if (bestmove == -1) {

bestmove = mw;

}

}

}

if (bestmove != -1) {

return bestmove;

}

// No move is totally satisfactory, try the first one that is open

for (int i = 0 ; i < 9 ; i++) {

int mw = moves[i];

if (((white & (1 << mw)) == 0) && ((black & (1 << mw)) == 0)) {

return mw;

}

}

// No more moves

return -1;

}

/**

User move.
@return true if legal
*/
boolean yourMove(int m) {
if ((m < 0) || (m > 8)) {
return false;
}
if (((black | white) & (1 << m)) != 0) {
return false;
}
black |= 1 << m;
return true;
}

/**

Computer move.
@return true if legal
*/
boolean myMove() {
if ((black | white) == DONE) {
return false;
}
int best = bestMove(white, black);
white |= 1 << best;
return true;
}

/**

Figure what the status of the game is.
*/
int status() {
if (won[white]) {
return WIN;
}
if (won[black]) {
return LOSE;
}
if ((black | white) == DONE) {
return STALEMATE;
}
return OK;
}

/**

Who goes first in the next game?
*/
boolean first = true;

/**

The image for white.
*/
Image notImage;

/**

The image for black.
*/
Image crossImage;

/**

Initialize the applet. Resize and load images.
*/
public void init() {
notImage = getImage(getCodeBase(), “images/not.gif”);
crossImage = getImage(getCodeBase(), “images/cross.gif”);

addMouseListener(this);
}

public void destroy() {

removeMouseListener(this);

}

/**

Paint it.
/
public void paint(Graphics g) {
Dimension d = getSize();
g.setColor(Color.black);
int xoff = d.width / 3;
int yoff = d.height / 3;
g.drawLine(xoff, 0, xoff, d.height);
g.drawLine(2xoff, 0, 2xoff, d.height);
g.drawLine(0, yoff, d.width, yoff);
g.drawLine(0, 2yoff, d.width, 2*yoff);

int i = 0;

for (int r = 0 ; r < 3 ; r++) {

for (int c = 0 ; c < 3 ; c++, i++) {

if ((white & (1 << i)) != 0) {

g.drawImage(notImage, c<em>xoff + 1, r</em>yoff + 1, this);

} else if ((black & (1 << i)) != 0) {

g.drawImage(crossImage, c<em>xoff + 1, r</em>yoff + 1, this);

}

}

}

}

/**

The user has clicked in the applet. Figure out where
and see if a legal move is possible. If it is a legal
move, respond with a legal move (if possible).
*/
public void mouseReleased(MouseEvent e) {
int x = e.getX();
int y = e.getY();

switch (status()) {

case WIN:

case LOSE:

case STALEMATE:

play(getCodeBase(), “audio/return.au”);

white = black = 0;

if (first) {

white |= 1 << (int)(Math.random() * 9);

}

first = !first;

repaint();

return;

}

// Figure out the row/column

Dimension d = getSize();

int c = (x * 3) / d.width;

int r = (y * 3) / d.height;

if (yourMove(c + r * 3)) {

repaint();

switch (status()) {
   case WIN:
 play(getCodeBase(), "audio/yahoo1.au");
 break;
   case LOSE:
 play(getCodeBase(), "audio/yahoo2.au");
 break;
   case STALEMATE:
 break;
   default:
 if (myMove()) {
     repaint();
     switch (status()) {
       case WIN:
 	play(getCodeBase(), "audio/yahoo1.au");
 	break;
       case LOSE:
 	play(getCodeBase(), "audio/yahoo2.au");
 	break;
       case STALEMATE:
 	break;
       default:
 	play(getCodeBase(), "audio/ding.au");
     }
 } else {
     play(getCodeBase(), "audio/beep.au");
 }
 }

} else {

play(getCodeBase(), “audio/beep.au”);

}

}

public void mousePressed(MouseEvent e) {
}

public void mouseClicked(MouseEvent e) {
}

public void mouseEntered(MouseEvent e) {
}

public void mouseExited(MouseEvent e) {
}

public String getAppletInfo() {

return “TicTacToe by Arthur van Hoff”;

}

}

1 Resposta

Topicos relacionados