wait() method

[pradeepta chopra]

K&B states"
When the Thread waits,it temporarily releases the lock for other threads to use,but it will nedd it again to continue execution.

synchronized(aObject)
{
 try{
     aObject.wait();
//the thread releases the lock and waits
// To continue,the thread needs the lock so it may be blocked until it gets //it.
    }
catch(InterruptedException e){}
}

Once the code has acquired lock on aObject it enters the try block and once wait() is executed,it is added to the waiting queue and the lock is released for other threads.


it waits until it is notified using

synchronized(this){notify();}

now what for the thread needs the lock again??has it left the synchronized code or not??

or it means that there may be other statements in the synchronized block to execute for which it again needs the lock

[Rekha Srinath]

A thread waits on an object till it gets the notification from that object.

what for the thread needs the lock again??has it left the synchronized code or not??

No, It has not yet left the synchronized code. It will be suspended on the wait call till it gets the notification. Once the notification is received, it will continue with the statement next to wait()...and to do this, the synchronized block of code requires a lock (object's lock)... This is because the code needs to know in what context / criteria it is supposed to run that synchonized block of code and that criteria is provided with the help of the object lock mechanism.