Thread confused

[Vierda Mila]

Dear Ranchers,

Below from Sun free assesment :

class NoGo implements Runnable {

private int i;

public synchronized void run () {

if (i%10 !=0) {i++;}

for (int x=0;x<10;x++,i++) {
if (x==4) Thread.yield();

}

System.out.println (i+" ");

}

public static void main (String[] args) {

NoGo n = new NoGo ();

for (int x=0;x<101;x++) {

new Thread (n).start();
}



}




}

When I compile above code, it gives me output value from 10 to 1010. Could somebody help me to understand how this code works, please? and thanks for your reply.

regards,
-Mila-

[yu yong]

Dear Vierda.
I dont understand what are you want to do about this code. Especially the line which is 'if (x==4) Thread.yield();' . I think this is useless in this code. Del this line will not change the result.

Changing the line 'sysout' with 'System.out.println("Thread " + Thread.currentThread().getId() + ": " + i );' maybe give some help you.

[Vierda Mila]

Dear Yu Yong,

Thanks for your reply. Do you mean since line 'if (x==4) Thread.yield();' is useless so the code continue looping 9 times or until its condition meet x<10 ??

regards,
-Mila-

[satishkumar janakiraman]

In your main method you are creating new threads in the for loop.when the
first thread starts running, the following operations will be performed.

Step 1:

i = 0 and (i%10 !=0) returns false, hence i++ value will not increase here.


Step 2:

now the for loop is getting executed in run method.
x = 0 and i = 0
(x == 4) returns false for first four iterations i.e from 0 to 3.
when x == 4, Thread 0 is suspended and Thread 1 or Thread 2 or Thread n will get the control depending on OS
and execute the for loop until x < 10. when x is greater than 10, control will go to SOP and prints the
value of i. i.e 10.

The above steps will continue until all your thread completes its work. In the mean time, the value of i will be
incremented for each iteration.


This is what exactly happening in your example.

[Vierda Mila]

Dear Satishkumar,

Thank you for your brief explanation.I got the point.

regards,
-Mila-

[Sandeep Bhandari]

The reason why we can say that first thread will be the one created first because the run method is declared as synchronized...
I don't think, deleting this keyword from run method will make any difference as far as output is concerned.