What do you expect the outcome to be when RunThread3 is executed? Compile and run i

Question

Consider the following Java classes:
```
import SomeThread3;
public class RunThreads3
{
public static void main (String[] args)
{
int originalThreadCount = Thread.activeCount( );
for (int i=0; i<10; i++) {
Thread p = new Thread(new SomeThread3());
p.start();
System.out.println("thread count=" +Thread.activeCount( ));
}

while (Thread.activeCount() > originalThreadCount ){
// loop until all child threads have exited.
}
System.out.println("finally, Count = " + SomeThread3.count);
}
}//end class RunThreads3

class SomeThread3 implements Runnable {
static int count=0;

SomeThread3() {
super();
}

public void run() {
update();
}

static public synchronized void update( ){
int myCount = count;

int second = (int)(Math.random( ) * 500);
try {
Thread.sleep(second);
}
catch (InterruptedException e) {
}

myCount++;
count = myCount;
System.out.println("count="+count+
"; thread count=" + Thread.activeCount( ));
}
} //end class SomeThread3
```

Answer 1

A synchronized method can only be run by one process/thread at a time, hence the ten child threads spawned by RunThreads3 will run the method consecutively, one at a time. The static variable count is therefore incremented successively, with its value changing from 0 to 10.

Here’s the outcome of a run on a system that runs Java 1.4. Note that the initial active thread count is 3.