Synchronized method in Java

Question

I have a question. In the following code, if a thread were blocked at wait statement, and another thread attempts to execute foo(), would the hello world message be printed? and Why?

synchronized foo(){
    system.out.println("hello world");
    .....
    wait();
    .....
}

Answer 1

Yes.

wait(); gives up the monitor, so yes , if Thread A is blocked in wait(); , Thread B would be able to enter foo and print hello world

Answer 2

For a thread to enter the method foo it needs to have a lock on the object (monitor) which contains the foo method. When the wait is executed the thread releases the lock on the monitor. So if another thread attempts to execute foo and (say it could acquire the lock) then it would print the "hello world" message.

Answer 3

It is also a best practice to wrap wait() invocation in a while . Reason: sporadic wake-up!