Another Thread ques

[Swati Gupta]

The question from Jqplus

 class MyThread extends Thread
{
public void run()
{
for(;    ;)    
{
System.out.println("running...");
}
}
}
public class TestClass6
{
public static void main(String args[]) throws Exception
{
MyThread mt = new MyThread();
mt.setDaemon(true);
mt.start();
mt.setDaemon(false);
}
} 

It should error out with exception as we are changing the status of the thread.
But it prints for sometimes and ends.I don't know its showing ;) but It is a infinite loop here
[ June 11, 2002: Message edited by: swati gupta ]
[ June 11, 2002: Message edited by: swati gupta ]
[ June 11, 2002: Message edited by: swati gupta ]
Edited by Corey McGlone: Turned off smilies to make the code more readable.
[ June 11, 2002: Message edited by: Corey McGlone ]

[Charlie Sturman]

if isAlive()
setDaemon() throws IllegalThreadStateException()
isAlive()
Tests if this thread is alive. A thread is alive if it has been started and has not yet died.
public final native boolean isAlive();
end of trail

[Francisco A Guimaraes]

but why we still see some output after the exception is thrown?
Francisco

[Francisco A Guimaraes]

 class MyThread extends Thread
{
public void run()
{
for(; ;) 
{
System.out.println("running...");
}
}
}
public class Test
{
public static void main(String args[]) throws Exception
{
MyThread mt = new MyThread();
mt.setDaemon(true);
mt.start();
mt.setDaemon(false);
}
}

output:
Exception in thread "main" java.lang.IllegalThreadStateException
at java.lang.Thread.setDaemon(Thread.java:1097)running..
running...
running...
running...
running...
running...
running...
running...
at Test.main(Test.java:20)
running...
running...
running...
running...
running...
running...
running...
running...
running...
running...
running...
running...
running...
running...
running...
running...
running...
running...
running...
[ June 12, 2002: Message edited by: Francisco A Guimaraes ]

[Jose Botella]

I guess because the deamon thread is still running for a while : for the lapse the JVM needs to check that no user thread is still running.

[Robert Alkire]

class MyThread extends Thread
{
static int i;
public void run() {
for(; {
System.out.println("running..."+ ++i);
}
}
}
public class MTest{
public static void main(String args[]) throws Exception
{
MyThread mt = new MyThread();
mt.setDaemon(true);
mt.start();
// runs longer when mt.setDaemon(false); is "commented in"
// only because it takes time to create and throw an exception
mt.setDaemon(false);
}
}