Why do threads run one at a time?

Question

[Newbie] Couldn't get help in another forum, so here goes. Tried this in Netbeans 3.5 then at home later in BlueJ, same thing. Thanks in advance!
I have written a small application to play with threads. I create 3 instances of a class and shoot each one off in a thread, but they all seem to run one at a time, not at the same time. I have posted the code below. The output I expect is something like this:
0T1
0T2
0T3
1T1
1T2
1T3
2T1
2T2
2T3
498T1
498T2
498T3
499T1
499T2
499T3
500T1
500T2
500T3
The T1 means threadstart1 wrote that line, the T3, means threadstart3 wrote the line, etc. I would expect to see these slightly out of order, too, knowing that the threads will process what they can, when they can. Instead, I see this:
0T1
1T1
2T1
500T1
0T2
1T2
2T2
500T2
0T3
1T3
2T3
500T3
It's in perfect numeric order, each completing before the next starts. What am I doing wrong?
//-------------dostuff.java
package delme2;
public class dostuff implements Runnable {
private String mtext;
public dostuff(String atext) {
mtext = atext;
public void run() {
int j;
String s;
//display 500 numbers
for (j=0; j<500; j++) {
//build the string
s = String.valueOf(j) + mtext;
//show the string
System.out.println(s);
//wait a bit before doing this again.
try {
Thread.sleep(10);
} catch (InterruptedException e) {
//--------------- delme2.java
package delme2;
public class delme2 {
public delme2() {
System.out.println("Thread demo:");
Runnable threadstart1 = new dostuff("T1");
Runnable threadstart2 = new dostuff("T2");
Runnable threadstart3 = new dostuff("T3");
Thread t1 = new Thread( threadstart1 );
Thread t2 = new Thread( threadstart2 );
Thread t3 = new Thread( threadstart3 );
t1.run();
t2.run();
t3.run();
public static void main(String[] args) {
delme2 mydelme2 = new delme2();
}

Answer 1

Okay, I'll play along. Having written a task scheduler in C (under tutorial, I admit), I think I qualify. A task scheduler has three jobs at all times.
1) Execute the code at hand.
2) Figure out when to stop executing the code at hand.
3) When stopped, figure out what code to execute next.
When executing a piece of code, there are different paradigms for determining when to stop and move on. Ideally, a cooperative multitasking system would have threads that relinquish timeslices or have some other method sprinkled throughout their code that indicates to the task scheduler that it's okay to move on to another piece of code. In my experience, that indicator is a Thread.Sleep() or equiavalent. when the thread.sleep() is encountered. The task scheduler has nothing to do for a whopping 10 MS. It could even take 15 or 20 ms if the next process in line takes that long. So what is it doing for 10 ms? It's not executing those other threads, which should be queued for their turn on step #3 as soon as I fire them off with a .run().
Now, I hope you can see that I've given this some thought and read about it, but I'm missing something. I can get a very similar project to work as I expect it to in .NET and in Delphi. The Java environment has something different about it that I haven't figured out. Here's the c# code that does EXACTLY what I want it to. All threads run at a same time, and I get 0,0,0,1,1,1,2,2,2,3,3,3,4,4,4, etc.. See the similarities?
          private void button1_Click(object sender, System.EventArgs e)
               lst.Items.Clear();
               ThreadStart start1 = new ThreadStart(runner);
               ThreadStart start2 = new ThreadStart(runner);
               ThreadStart start3 = new ThreadStart(runner);
               Thread t1 = new Thread(start1);
               Thread t2 = new Thread(start2);
               Thread t3 = new Thread(start3);
               t1.Start();
               t2.Start();
               t3.Start();
          private void runner()
               string s;
               for (int j=0; j<500; j++)
                    s = j.ToString();
                    lst.Items.Add(s);
                    Thread.Sleep(10);
          }