wait(), notify(), notifyAll() doubt

[Gari Jain]

class Reader extends Thread
{
Calculator c;

public Reader(Calculator calc)
{
c=calc;
}
public void run()
{
synchronized(c){
try{
System.out.println("Waiting for calculation...");
c.wait();
}catch(InterruptedException e){}
System.out.println(Thread.currentThread().getName()+":Total is: "+c.total);
}
}
public static void main(String args[])
{
Calculator calculator=new Calculator();
Reader r1=new Reader(calculator);
r1.setName("Reader1");
r1.start();
Reader r2=new Reader(calculator);
r2.setName("Reader2");
r2.start();
Reader r3=new Reader(calculator);
r3.setName("Reader3");
r3.start();
calculator.start();
}
}

class Calculator extends Thread
{
int total;
public void run()
{
synchronized(this)
{
for(int i=0;i<100;i++)
{
total+=i;
}
notify();
}
}
}

The notify() method is used to send a signal to one and only one of the
threads that are waiting in that same object's waiting pool.

then when i run this code..how come all the readers are notified?

[Arjun Srivastava]

Gari Jain wrote:
wait(), notify(), notifyAll(),serialization

These topics are no longer in syllabus of SCJP6, you can skip these topics if you are preparing for exam.

[Deepak Bala]

Please QuoteYourSources

[Vinoth Kumar Kannan]

Gari, if you still want to know the reason for that kind of behavior, you can take a look at this thread. See if it helps.

[Ireneusz Kordal]

Arjun Srivastava wrote:

Gari Jain wrote:
wait(), notify(), notifyAll(),serialization

These topics are no longer in syllabus of SCJP6, you can skip these topics if you are preparing for exam.

See this thread: https://coderanch.com/t/509640/java-programmer-SCJP/certification/Cleared-OCPJP-morning
Someone got 4 questions on synchronization/wait/notify on the exam this morning.

[Arjun Srivastava]

Ireneusz Kordal wrote:
See this thread
Someone got 4 questions on synchronization/wait/notify on the exam this morning.

have already saw, but they are just statements(true or false), not the codes related to wait and notify.
still it helps others to focus on these topics too.

[Divyeshh Patel]

Gari Jain wrote:
The notify() method is used to send a signal to one and only one of the
threads that are waiting in that same object's waiting pool.

then when i run this code..how come all the readers are notified?

Gari,
If you haven't already figured it out, even the notify() call in this program is superfluous.
You can run the program after removing that call and you will get the same result.

[Anton Brass]

To spare you the reading of the threads, it seems that after run() finishes notifyAll() is triggered. Your Calculator class is extending Thread and using the run() method. After finishing its calculations the run() method ends and notifyAll() is triggered automatically.