[Java] wait() and notify()

if we call the wait() of object a :
  a.wait() ---> this will block the thread and release the lock of a

if we call the notify() of object a :
  a.notify() --> will disblock one of the blocked threads (randomly)

1 > If we use the synchronized  we don't have to use wait()/notify()
2 > If we use the wait()/notify() we have to use synchronized :
                                       ( wait/notify should be in synchronized)

we can find wait()/notify() is not from the thread part, it's from class Object!

ex : transaction of an bank account :

public class Bank{
           float account[ACCOUNT_NUM];
           ..............
           public synchronized void transfer(int from, int to, float amount){
                       while( account[from]  < amount){
                                     wait();
                        }
                        account[from] -=amount;
                        account[to] +=amount;
                        notifyAll();
           }
}

use while() rather than if, we can do the loop
use notifyAll() is better than notify()