Why doesn't thread wait for notify()
? The thread starts and then goes to the waiting pool, but it proceeds to execute after that moment.
public class JavaApplication2 {
public static void main(String [] args) {
ThreadB b = new ThreadB();
synchronized(b) {
b.start();
try {
System.out.println("1");
b.wait();
} catch (InterruptedException e) {}
System.out.println("Total is: " + b.total);
}
}
}
class ThreadB extends Thread {
int total;
@Override
public void run() {
synchronized(this) {
total += 1;
//notify();
}
}
}
You are synchronizing on the thread object itself, which is wrong usage. What happens is that the dying thread-of-execution always calls notify
on its Thread
object: Thread.join
relies on this. Therefore it is clear why you get the same behavior with and without your own notify
in there.
Solution: use a separate object for thread coordination; this is the standard practice.