Explanation for the code

Question

class ThreadA {
public static void main(String [] args) {
ThreadB b = new ThreadB();
b.start();
synchronized(b) {
try {
System.out.println("Waiting for b to complete...");
b.wait();
} catch (InterruptedException e) {}
System.out.println("Total is: " + b.total);
class ThreadB extends Thread {
int total;
public void run() {
synchronized(this) {
for(int i=0;i<100;i++) {
total += i;
notify();
}can anyone please explain me the code flow of this particular program n how does wait n notify work inb this..im a bit confused.thankx in adv.

Answer 1

sowme wrote:
kajbj wrote:
sowme wrote:
its just an example to illustrate the use of wait and notify and i think i havent mentioned any word saying this code is a good one or safe to use ..but i would like to know why it is bad and unsafe.Total needs to be volatile. The main thread can otherwise print the wrong value. There's also a possibility that the program never terminates, and that can happen if thread B gets the lock before the main thread gets the lock. (That is, notify is called before the main thread has invoked wait).
but when will this happen that is thread B gets the lock before the main thred gets the lock?i dint understand can u please explain.The threads are sharing the cpu time, and thread B can start executing after the call to b.start(). Nothing says that the main thread will reach the syncrhonized block before thread b does.
Kaj