Difference Analysis Between Java multi-threaded consumer y and consumer yall

When a thread enters wait, it must wait for other threads notify/notifyall and use notifyall to wake up.
All the threads in the wait status re-enter the lock contention queue, and notify can only wake up one. Note: at any time, only one thread can obtain the lock, that is, only one thread can run the code in synchronized. policyall only allows the thread in the wait to re-compete for the lock, however, only one lock is obtained and executed.

So what are the actual differences between policy and policyall?
The main difference is that running y is not easy to cause deadlocks, as shown in the following example.

Copy codeThe Code is as follows: public synchronized void put (Object o ){

While (buf. size () = MAX_SIZE ){

Wait (); // called if the buffer is full (try/catch removed for brevity)

}

Buf. add (o );

Y (); // called in case there are any getters or putters waiting

}

Copy codeThe Code is as follows: public synchronized Object get (){

// Y: this is where C2 tries to acquire the lock (I. e. at the beginning of the method)

While (buf. size () = 0 ){

Wait (); // called if the buffer is empty (try/catch removed for Brey)

// X: this is where C1 tries to re-acquire the lock (see below)

}

Object o = buf. remove (0 );

Y (); // called if there are any getters or putters waiting

Return o;

}

Therefore, unless you are very sure that there is no problem with policyall, you can use policyall in most cases.

For more details, see:
Http://stackoverflow.com/questions/37026/java-notify-vs-notifyall-all-over-again