Java并发-如何正确锁定和释放线程

Question

I would like to understand how do i properly use wait and notify without Semafor or CountdownLatch. lets have a simple example

Response call(long[] l)
{
   final Response r = new Response();
   Thread t = Thread.currentThread(); //get current thread
   thread2(l,s -> {
       response.setObject(s);
       t.notify(); //wake up first thread 
   });
   Thread.currentThread().wait(); //wait until method thread2 finishes
   return response;
} 
void thread2(long[] l, Consumer c)
{
    //start new thread and call
    c.accept(resultobject);
}

Is my behavior acceptable? is it required to put .notify method in a synchronized block?

Answer 1

Yes it is required to put notify into a synchronized block . The main logic is the following:

Pseudo code of the threads waiting for a given state of an Object:

synchronized(mutex) {
    while (object state is not the expected one) {
        mutex.wait();
    }
    // Code here that manipulates the Object that now has the expected state
}

Pseudo code of the threads that modify the state of the Object and want to notify other threads:

synchronized(mutex) {
    // Code here that modifies the state of the object which could release
    // the threads waiting for a given state
    mutex.notifyAll();
}