I'm trying to run four threads. run() method has a for loop that loops 10 times.In each loop the shared resource "x" is increment by 1. When all threads die, the for loop should have run 4x10 =40 times and x value should equal 40.
That is not happening in all runs of the my code.Each time I run the code it prints a different value of x.Most of the output values of x range from 33 to 40.
Why is it not 40 in every run? Does that mean some for loop loops are being skipped? Is it caused due being blocked?
NOTE : this does not happen when sleep() is removed. It prints 40 every single time.
My code :
public class MyThreadImplementsRunnable implements Runnable{
int x =0;
public void run() {
for(int i=0;i<10;i++){
x = x+1;
try {
Thread.sleep(1);
} catch (InterruptedException e) {
System.out.println("exception");
e.printStackTrace();
}
}
}
public static void main(String[] args) {
MyThreadImplementsRunnable m = new MyThreadImplementsRunnable();
Thread t1 = new Thread(m,"first");
Thread t2= new Thread(m,"second");
Thread t3= new Thread(m,"third");
Thread t4= new Thread(m,"fourth");
t1.start();
t2.start();
t3.start();
t4.start();
//To make sure not to go the next statement unless all threads die
while(t1.isAlive()|| t2.isAlive()|| t3.isAlive()||t4.isAlive()){
}
//After all threads die
System.out.println("now all threads are dead");
//value of the shared resource x after all threads exit
System.out.println(m.x);
}
}
Some test runs gave the following results :
Output:
now all threads are dead
34
Output:
now all threads are dead
33
