問題描述
遊戲線程問題 (Issues with threads in game)
我一直在嘗試使用一些基本的多線程來製作一個基本的井字遊戲，但不知何故，兩個線程都可以訪問同步語句，這讓我很困惑。
這是代碼：
import java.util.*;
public class TicTacToe extends Thread {
static char[][] map = new char[3][3];
static char notsCrosses;
static volatile boolean gameFinish = false;
public TicTacToe(String n){
super(n);
}
public TicTacToe(){
}
public synchronized String pickPosition(int x){
switch (x){
case 1: map[0][0] = notsCrosses; return "00";
case 2: map[0][1] = notsCrosses; return "01";
case 3: map[0][2] = notsCrosses; return "02";
case 4: map[1][0] = notsCrosses; return "10";
case 5: map[1][1] = notsCrosses; return "11";
case 6: map[1][2] = notsCrosses; return "12";
case 7: map[2][0] = notsCrosses; return "20";
case 8: map[2][1] = notsCrosses; return "21";
case 9: map[2][2] = notsCrosses; return "22";
}
return null;
}
public void run() {
if (this.getName() == "player1") {
notsCrosses = 'X';
} else {
notsCrosses = 'O';
}
Scanner input = new Scanner(System.in);
synchronized (this) {
while (!gameFinish) {
try {
System.out.print(this.getName() + " Enter the position (1‑9): ");
int position = input.nextInt();
pickPosition(position);
System.out.print("h");
printMaze();
int yCood = Integer.parseInt(pickPosition(position).substring(0, 1));
int xCood = Integer.parseInt(pickPosition(position).substring(1, 2));
if (hasWon(map, xCood, yCood)) {
System.out.println("You win! " + this.getName());
gameFinish = true;
}
notify();
wait();
} catch (InterruptedException i) {
}
}
}
}
public static void main(String[] args) {
for(int i=0; i<map.length; i++){
for(int j=0; j<map[i].length; j++){
map[i][j] = '‑';
}
}
new TicTacToe().printMaze();
TicTacToe player1 = new TicTacToe("player1");
TicTacToe player2 = new TicTacToe("player2");
player1.start();
player2.start();
}
public synchronized void printMaze(){
for(int i=0; i<map.length; i++){
if(i==0) {
for (int x = 0; x < 3; x++) {
System.out.print("‑‑‑");
}
System.out.println();
}
for(int j=0; j<map[i].length; j++) {
System.out.print("|");
System.out.print(map[i][j]);
System.out.print("|");
}
System.out.println();
for(int x=0; x<3; x++) {
System.out.print("‑‑‑");
}
System.out.println();
}
}
public synchronized boolean hasWon(char[][] m,int xCood, int yCood){
if(checkRow(m,yCood) || checkColumn(m,xCood) || checkDiagonal(m,xCood,yCood)){
return true;
}
return false;
}
public synchronized boolean checkRow(char[][] m,int yCood){
for(int i=0; i<3; i++){
if(map[yCood][i] != notsCrosses){
return false;
}
}
return true;
}
public synchronized boolean checkColumn(char[][] m,int xCood){
for(int i=0; i<3; i++){
if(map[i][xCood] != notsCrosses){
return false;
}
}
return true;
}
public synchronized boolean checkDiagonal(char[][] m,int xCood, int yCood){
if(map[0][0]==notsCrosses && map[1][1]==notsCrosses && map[2][2]==notsCrosses){
return true;
}
else if(map[2][0]==notsCrosses && map[1][1]==notsCrosses && map[0][2]==notsCrosses){
return true;
}
return false;
}
}
我在 run 方法中使用 synchronize 語句，我想做的只是一次只允許一個線程（播放器）訪問該代碼並檢查 volatile 變量“遊戲完成”。
參考解法
方法 1:
You have two bugs:
You have two players, each of which synchronize on themselves. That won't work. You need to synchronize on some single thing that is shared.
Nowhere does your code keep track of which player's turn it is. So your code has no idea when to stop waiting. It just guesses and may guess wrong.
(by Mohammad Rizwaan、David Schwartz)