我在Java 7应用程序上实现Synchronized接口时遇到了问题。我认为问题可能在于我使用静态final数组实例化多个对象,该数组在同步方法中被写入。似乎线程没有识别监视器?我能做我想做的事情吗?还是需要一种具有数组和writeIndex增量器的缓冲对象?(如果有帮助,则代码位于https://github.com/dschaper/CS112_Dan_Schaper/tree/master/Week14/Labs,这不是作业,只是一个非分级实验室。)
public class SingleDice extends Dice implements Runnable {
String threadName;
private static final int[] valuesArray = new int[9];
private static int writeIndex = 0;
public SingleDice(String tName) {
super(1);
threadName = tName;
}
public synchronized void add(int value) {
int pos = writeIndex;
System.out.printf("%s starting sync add(%d), writeIndex = %d\n",
Thread.currentThread().getName(), value,
writeIndex);
valuesArray[pos] = value;
System.out.printf("%s wrote %d to index %d\n",
Thread.currentThread().getName(), value, writeIndex);
++writeIndex;
System.out.printf("Next writeIndex %d\n", writeIndex);
}
@Override
public void run() {
for (int i = 0; i < 3; i++) {
add(super.Throw());
}
}
}
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class SyncDiceExecutor {
public static void main(String[] args) {
System.out.println("Creating newCachedThreadPool");
SingleDice SD1 = new SingleDice("SD1");
SingleDice SD2 = new SingleDice("SD2");
SingleDice SD3 = new SingleDice("SD3");
ExecutorService executor = Executors.newCachedThreadPool();
executor.execute(SD1);
System.out.printf("Starting Thread SD1 %s\n", executor.toString());
executor.execute(SD2);
System.out.printf("Starting Thread SD2 %s\n", executor.toString());
executor.execute(SD3);
System.out.printf("Starting Thread SD3 %s\n", executor.toString());
executor.shutdown();
System.out.printf("Execeutor shutdown called: %s\n", executor.toString());
}
}
输出
Creating newCachedThreadPool
Starting Thread SD1 java.util.concurrent.ThreadPoolExecutor@544ec1[Running, pool size = 1, active threads = 1, queued tasks = 0, completed tasks = 0]
pool-1-thread-1 starting sync add(4), writeIndex = 0
pool-1-thread-2 starting sync add(4), writeIndex = 0
Starting Thread SD2 java.util.concurrent.ThreadPoolExecutor@544ec1[Running, pool size = 2, active threads = 2, queued tasks = 0, completed tasks = 0]
pool-1-thread-2 wrote 4 to index 0
pool-1-thread-1 wrote 4 to index 0
pool-1-thread-3 starting sync add(4), writeIndex = 1
Next writeIndex 1
pool-1-thread-2 starting sync add(6), writeIndex = 2
Starting Thread SD3 java.util.concurrent.ThreadPoolExecutor@544ec1[Running, pool size = 3, active threads = 3, queued tasks = 0, completed tasks = 0]
pool-1-thread-2 wrote 6 to index 2
Next writeIndex 3
pool-1-thread-3 wrote 4 to index 2
Next writeIndex 4
Next writeIndex 2
pool-1-thread-3 starting sync add(1), writeIndex = 4
pool-1-thread-2 starting sync add(6), writeIndex = 3
Execeutor shutdown called: java.util.concurrent.ThreadPoolExecutor@544ec1[Shutting down, pool size = 3, active threads = 3, queued tasks = 0, completed tasks = 0]
pool-1-thread-2 wrote 6 to index 4
Next writeIndex 5
pool-1-thread-3 wrote 1 to index 4
Next writeIndex 6
pool-1-thread-1 starting sync add(3), writeIndex = 4
pool-1-thread-3 starting sync add(1), writeIndex = 6
pool-1-thread-1 wrote 3 to index 6
pool-1-thread-3 wrote 1 to index 6
Next writeIndex 8
Next writeIndex 7
pool-1-thread-1 starting sync add(1), writeIndex = 8
pool-1-thread-1 wrote 1 to index 8
Next writeIndex 9
Process finished with exit code 0
public synchronized void add(int value) { synchronized(this) ... }
,就像我在上面编码的那样?(正如 @hyde 指出的那样)我只需要显式地将 (this) 更改为 (SingleDice.class)。 - SonOfAMotherlessGoatsynchronized
放在方法签名中,本质上与在方法内部使用synchronized(this) {method body}
是相同的。因此,您可以从签名中删除synchronized
,并在方法体周围添加synchronized(SingleDice.class) { ... }
。 - fpwsynchronized
关键字,以避免餐桌哲学家问题。 - fpw