From textbook, I was told to implement Thread code, the run() method
need to be overriden. However, I just found below code from one java
programmer exam web site that said the reverse.

Below program compiled & ran without error. But I would like to ask if
public void start() was replaced by public void run(), how the
program's behaviour got changed ? Did the difference laid at separate
stacks being created for thread instances 'first' & 'second' if public
void run() implemented instead of public void start() ? From program
execution output I didn't see the difference. :)

public class Holt extends Thread {
 private String sThreadName;
 public static void main(String argv[]) {
   Holt h = new Holt();
   h.go();
 }
 Holt() {}
 Holt(String s) {
   sThreadName = s;
 }
 public String getThreadName() {
   return sThreadName;
 }
 public void go() {
   Holt first = new Holt("first");
   first.start();
   Holt second = new Holt("second");
   second.start();
 }
 public void start() {
   for (int i=0; i<2; i++) {
     System.out.println(getThreadName()+i);
     try {
       Thread.sleep(100);
     } catch (InterruptedException e) {
       System.out.println(e.getMessage());
     }
   }
 }
}