我正在阅读有关 java Thread 的主题。
还有一个例子:
import java.util.Vector;
class Producer extends Thread {
static final int MAXQUEUE = 5;
private Vector messages = new Vector();
@Override
public void run() {
try {
while (true) {
putMessage();
//sleep(5000);
}
} catch (InterruptedException e) {
}
}
private synchronized void putMessage() throws InterruptedException {
while (messages.size() == MAXQUEUE) {
wait();
}
messages.addElement(new java.util.Date().toString());
System.out.println("put message");
notify();
//Later, when the necessary event happens, the thread that is running it calls notify() from a block synchronized on the same object.
}
// Called by Consumer
public synchronized String getMessage() throws InterruptedException {
notify();
while (messages.size() == 0) {
wait();//By executing wait() from a synchronized block, a thread gives up its hold on the lock and goes to sleep.
}
String message = (String) messages.firstElement();
messages.removeElement(message);
return message;
}
}
class Consumer extends Thread {
Producer producer;
Consumer(Producer p) {
producer = p;
}
@Override
public void run() {
try {
while (true) {
String message = producer.getMessage();
System.out.println("Got message: " + message);
//sleep(200);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public static void main(String args[]) {
Producer producer = new Producer();
producer.start();
new Consumer(producer).start();
}
}
并且作者说:
A possible output sequence:
Got message: Fri Dec 02 21:37:21 EST 2011
put message
put message
put message
put message
put message
Got message: Fri Dec 02 21:37:21 EST 2011
Got message: Fri Dec 02 21:37:21 EST 2011
Got message: Fri Dec 02 21:37:21 EST 2011
Got message: Fri Dec 02 21:37:21 EST 2011
Got message: Fri Dec 02 21:37:21 EST 2011
put message
put message
put message
put message
put message
Got message: Fri Dec 02 21:37:21 EST 2011
Got message: Fri Dec 02 21:37:21 EST 2011
Got message: Fri Dec 02 21:37:21 EST 2011
但是当我运行这段代码时,我得到了这个结果:
put message
put message
put message
put message
put message
put message
Got message: Tue Sep 24 16:44:59 CST 2013
Got message: Tue Sep 24 16:45:00 CST 2013
put message
Got message: Tue Sep 24 16:45:00 CST 2013
put message
Got message: Tue Sep 24 16:45:00 CST 2013
put message
..............
问题是什么?
任何人都可以为我解释一下吗?