Java 线程问题

Question

public class ThreadTest {

/**

• @param args */ public static Integer ticket = 1;

public static void main(String[] args) {

new Thread() {

@Override
public void run() {

for (int i = 0; i < 50; i++)
loopThread(1);
}

}.start();

for (int i = 0; i < 50; i++)
loopThread(0);

}

public static void loopThread(int id) {

// main
synchronized (ticket) {
if (id == ticket && ticket == 0) {

System.out.println("loop 100 times for main thread");

// switch the ticket to sub thread
ticket = 1;
ticket.notify();

} else if (id == ticket && ticket == 1) {

System.out.println("loop 10 times for sub thread");

// switch the ticket to main thread

ticket=0;
ticket.notify();

} else {
try {
ticket.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}

求教这个问题错在哪？错误是

loop 10 times for sub thread
Exception in thread "Thread-0" java.lang.IllegalMonitorStateException
at java.lang.Object.notify(Native Method)
at ThreadTest.loopThread(ThreadTest.java:45)
at ThreadTest$1.run(ThreadTest.java:16)

请不吝赐教，拜谢。。。。

Answer 1

比如
System.out.println("loop 100 times for main thread");

// switch the ticket to sub thread
ticket = 1;

此处ticket又是个新对象

所以接着调用 ticket.notify(); 会抛刚才的异常 即锁对象不是原来的了

java.lang.IllegalMonitorStateException异常 原因就是当前线程没有获得对象的锁。

此处建议使用AtomicInteger 加 自身的自增完成